paging | A small set of utilities to paginate your data in Go | Widget library
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kandi X-RAY | paging Summary
A small set of utilities to paginate your data in Go
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Trending Discussions on paging
QUESTION
I get it that if a page has been accessed it'll have the Access bit set, and if has been written to, the Dirty bit will also be set. But it's unclear to me how these bits affect the TLB/TLB caching? Also OSDEV has the following paragraph
When changing the accessed or dirty bits from 1 to 0 while an entry is marked as present, it's recommended to invalidate the associated page. Otherwise, the processor may not set those bits upon subsequent read/writes due to TLB caching.
In what cases would you change the dirty and access bits from 1 to 0?
...ANSWER
Answered 2022-Mar-23 at 09:51In what cases would you change the dirty and access bits from 1 to 0?
If the OS is running low on memory it'll want to free some pages (e.g. send the page's data to swap space so it can use the physical memory for something else). Often this will be based on "least recently used", but the CPU only has 1 "accessed" flag for each page, so to work around that the OS checks the accessed flags periodically and clears them back to zero so it knows (roughly) how long ago a page was accessed and not just if it was/wasn't accessed. It's a little like "if(page->accessFlag == 1) { page->accessFlag = 0; page->time_since_access = 0; } else { page->time_since_access++; }
".
For the dirty flag, consider a read/write memory mapped file, or a write-back disk cache. A program modifies data in memory (causing the dirty flag to be set); then when the disk drive has nothing better to do the OS might find pages with the dirty flag set, write them to disk, and clear the dirty flag/s back to zero (so the same page doesn't get written to disk again for no reason next time).
How does the Dirty and Access bits affect the TLB?
It's more the opposite - the TLB effects the flags (and the flags don't effect the TLB).
When a CPU sets the dirty or accessed flags it does an atomic update of memory to guard against race conditions (e.g. other CPUs modifying or checking the same page table entry at the same time), and atomic updates are somewhat expensive. To reduce/avoid these atomic writes a CPU can (and most likely will) cache the page's accessed and dirty flags in the TLB entry so that the atomic write can be skipped if the CPU wants to set the flag/s but the TLB entry says they're already set anyway. If the TLB entry is wrong (e.g. because the OS changed the accessed or dirty flags in memory but didn't invalidate the TLB entry) then the CPU can skip atomic writes that were needed by the OS. This can cause data corruption (e.g. OS assuming that a page's contents in memory don't need to be written to disk because the dirty flag wasn't set).
QUESTION
I've updated my android application to target Android S and was made to add
...ANSWER
Answered 2021-Oct-20 at 13:35The fix was to also increase paging androidx.paging:paging-runtime-ktx
to beta01
QUESTION
I have been developing a personal application to build a finance app. At the moment I'm creating an Onboarding screen, with is successfully working. Although I want to add some styles to it, I have created an animated paginator, but I want to make the last page indicator turn into a Touchable button.
At the moment the paginator looks like this:
I want that last animation turn into a button.
This is my code for Paginator:
ANSWER
Answered 2022-Mar-08 at 20:08The key points were:
- When we scroll from
n-1
th ton
th page,- All indicators except nth need to be adjusted. The adjustment could be either of
- Shrink content+margin of all other indicators to 0 width. ( preferred )
- Move all indicators to left by calculated amount.
- The
n
th element should grow to occupy full width. The contents should also change opacity from0
to1
.
- All indicators except nth need to be adjusted. The adjustment could be either of
With this points in mind, it should be easy to understand following changes in Paginator code.
QUESTION
Is there a way to use c++20s concepts to check that a value meets some requirements?
Lets say I am writing some sort of container that uses paging and i want to make the page size a template parameter.
...ANSWER
Answered 2022-Feb-19 at 13:01The easiest way would be to constrain the template parameters of the class.
QUESTION
I have error like this after trying to build my apps in Emulator
/Users/joel/.gradle/caches/transforms-3/06231cc1265260b25a06bafce7a4176f/transformed/core-1.7.0-alpha02/res/values/values.xml:105:5-114:25: AAPT: error: resource android:attr/lStar not found.
I don't know what causes this error. After digging some answer which has similarly error (but in flutter) Problem. But still not solved my issue.
I have this dependency in my project
...ANSWER
Answered 2021-Sep-28 at 17:18I managed to fix this by upgrading compileSdk to 31 and kotlin gradle plugin to 1.5.10
QUESTION
Ok then. I have this code and is just for practice so it could be a bit messy (please ignore the cammelCase convention or bad practices unless they are the cause of the problem, beacause I've already take note of it), howerver i'm going to describe what it does and I'll show the code.
I have this componet that is rendered without data at first time, then when the users click a button (in a parrent component) an API it's called (also in the parrent) and the response is sended to this problematic component through props. After de data from the API is recived (props.rows), a useEffect is executed to format this data and store it in state (Rows). When Rows value changes, another useEffect should be executed and manipulate Rows (without mutating it) to create another kind of data (TotalPages). The thing is that when I call setTotalPages() this produce an infinite loop and I get the error Uncaught Error: Too many re-renders. React limits the number of renders to prevent an infinite loop.
I'll show the code now
This is the problematic component
...ANSWER
Answered 2022-Feb-15 at 03:10QUESTION
i'm trying to get media fields from the instagram api and i'm getting this error
...ANSWER
Answered 2022-Feb-01 at 18:30According to the documentation : https://developers.facebook.com/docs/instagram-basic-display-api/reference/media ,every field is a String
QUESTION
I'm currently reading the Understanding the Linux kernel Third Edition and I'm on chapter 2 about memory addressing. At first the book covers paging in 32 bit, PAE 32 bit, and PSE (we are talking about x86 here). More specifically the anatomy of linear address and what bits are for what tables, offsets, etc... I started to get confused about the paging model in Linux. At one moment the book was talking about directory, table, and offset bits of a linear address (PDPT table for PAE) and next I was thrown into the world of "Linux" paging. Now with the Linux paging they talk about Global, Upper, and Middle tables with table and offset? I don't see how the x86 MMU paging relates to this new Linux model at all. If the MMU is in charge of translating (paging) addresses, why does the kernel need this paging model as well? It just seems like the kernel should just leave it up to the MMU. If anyone could elaborate on why the kernel has this, that would be great!
I understand that the MMU has to translate address based on the tables that the kernel manages. So, the MMU is in charge of address translation (from memory accesses from a process running on a core) but the kernel is not! So why do we have this Global, Upper, and Middle tables with table and offset stuff?
Or maybe this Linux paging model is more abstract than I'm making it to be! Maybe the idea of this kernel page table is not really a table but a set of kernel macros specifying the properties of the many levels of page directories/tables that the kernel has to maintain! For example, the PGD_SIZE
, PUD_SIZE
and the other SIZE
macros (along with the SHIFT
and MASK
macros) specify the different properties of the levels of paging. Based on these macros (of course there are other macros) the kernel can generate the correct page tables in memory? This Linux paging model can adjust the SHIFT macros based on the specific architecture (more specifically the bit layout of linear addresses on the specific architecture)?
ANSWER
Answered 2022-Feb-05 at 04:45At one moment the book was talking about directory, table, and offset bits of a linear address (PDPT table for PAE) and next I was thrown into the world of "Linux" paging. Now with the Linux paging they talk about Global, Upper, and Middle tables with table and offset?
Yeah... this can get pretty confusing pretty quickly. When the Intel manual talks about paging, page table entries at different levels are called:
- PML5E = Page Map Level 5 Entry
- PML4E = Page Map Level 4 Entry
- PDPTE = Page Directory Pointer Table Entry
- PDE = Page Directory Entry
- PTE = Page Table Entry
As you can deduce from the above names, x86 supports up to 5 levels of page tables (on modern processors). There are different paging models that can be used on any given processor based on its capabilities, for example 32bit without PAE paging uses 2-level page tables: we only have PDEs and PTEs, and CR3 points to a page directory). More page table levels can be set up and used, and in that case we begin talking about PDPTEs (for 3-level paging), PML4Es (4-level paging) and PML5Es (5-level paging).
Now of course page tables are pretty much an ubiquitous concept amongst most CPU architectures, not only x86. However each architecture has its specific way of naming page table entries at different levels. Linux supports a lot of different architectures, so it gives page table entries some "generic" names:
pgd_t
= Page Global Directory entryp4d_t
= Page level-4 Directory entrypud_t
= Page Upper Directory entrypmd_t
= Page Middle Directory entrypte_t
= Page Table Entry
Now this is where it could get confusing. There is a major distinction to be made between Intel's and Linux's naming convention. Regardless of the number of levels of page tables, for Linux the Page Global Directory always represents the root (so pgd_t
always represents highest-level entries):
- For 5-level paging, the correspondence between Intel names and Linux names is just plain and simple:
pgd_t
:PML5E,p4d_t
:PML4E,pud_t
:PDPTE,pmd_t
:PDE,pte_t
:PTE. - For 4-level paging, we have
pgd_t
:PML4E, andp4d_t
is unnecessary, so it essentially becomes an alias forpgd_t
(before 5-level paging support, there simply was nop4d_t
at all). - Analogously, for 3-level paging we have
pgd_t
:PDPTE, and for 2-levelpgd_t
:PDE.
If the MMU is in charge of translating (paging) addresses, why does the kernel need this paging model as well? It just seems like the kernel should just leave it up to the MMU.
Well, yeah, the kernel does leave the work to the MMU. What we are talking about here are just naming conventions. Linux does not use another paging model on top of the one already used by the MMU, it just has a different and more generic way of naming things, that's it.
Maybe the idea of this kernel page table is not really a table but a set of kernel macros specifying the properties of the many levels of page directories/tables that the kernel has to maintain!
[...]
Based on these macros (of course there are other macros) the kernel can generate the correct page tables in memory? This Linux paging model can adjust the SHIFT macros based on the specific architecture (more specifically the bit layout of linear addresses on the specific architecture)?
Yes, yes and yes. You got it. That's exactly the rationale behind this naming abstraction. The kernel only calls things one way, but adjusts macros (e.g. PMD_OFFSET
), types (e.g. pmd_t
), and logic based on the underlying architecture.
QUESTION
I using Infinite Scroll Pagination plugin in my flutter's app. I need also using SilverAppBar in my page. This is my code:
...ANSWER
Answered 2021-Dec-20 at 04:09it's happening because tabBarView
needs normal box children
rather than slivers
because it uses pageview by default as you can read here in official documentation.
if you use normal list instead of slivers like below it will solve the problem:
QUESTION
I'm trying to follow this documentation here concerning how to unit test a PagingData stream on which you're applying transforms. The code I am using is similar:
...ANSWER
Answered 2021-Dec-12 at 21:23the following works here:
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