vinyl: implement page cache #7602

quaiion · 2022-08-24T11:53:14Z

No description provided.

CuriousGeorgiy · 2022-09-29T12:15:22Z

src/box/vy_run.c

@@ -250,7 +250,7 @@ vy_page_info_create(struct vy_page_info *page_info, uint64_t offset,
 {
 	memset(page_info, 0, sizeof(*page_info));
 	page_info->offset = offset;
-	page_info->unpacked_size = 0;
+	page_info->unpacked_size = 0;		//temp/ why?..


Leaving this line untouched

CuriousGeorgiy · 2022-09-29T12:19:41Z

src/box/vy_run.c

@@ -710,6 +715,8 @@ vy_page_new(const struct vy_page_info *page_info)
 			 "load_page", "page cache");
 		return NULL;
 	}
+	page->ri_refs = 0;			//temp/ maybe should already set to 1


Looks okay.

Currently removing any refs-related code so this won't be presented in the final version anyway

CuriousGeorgiy · 2022-09-29T12:26:17Z

src/box/vy_run.c

+vy_page_ref(struct vy_page *page)
+{
+	assert(page != NULL);
+	assert(page->ri_refs != 0);


Looking at our other reference counted objects, this looks strange. You should rather call it after vy_page_new.

Currently removing any refs-related code so this function won't be presented in the final version anyway

CuriousGeorgiy · 2022-09-29T12:34:30Z

src/box/vy_run.c

+ * Decrease memory-stored page's reference counter.
+ */
+static inline void
+vy_page_unref(struct vy_page_info *page_info)


The API asymmetry looks weird. Please make it symmetric and probably rename it to vy_page_info_page_*ref.

Currently removing any refs-related code so this function won't be presented in the final version anyway

CuriousGeorgiy · 2022-09-29T12:36:10Z

src/box/vy_run.c

+ * End iteration and unref cached pages.
+ */
+static void
+vy_run_iterator_stop(struct vy_run_iterator *itr)


Why did you move it here?

It was moved here because it needed the vy_page_unref() function to be defined. Now we abandon using refs, so it will be moved back.

CuriousGeorgiy · 2022-09-29T14:40:04Z

src/box/vy_run.c

+ * percentage of pages in current page cache is deleted.
+ */
+static void										//temp/ maybe should add error codes (what errors?..)
+vy_page_cache_mem_cutback(struct vy_run_env *run_env, uint8_t del_percent)


Let's use percentage instead of ratio.

Guess you meant "ratio instead of percentage". Anyway, we already abandoned the percentage-based cutbacks and switched to a classic "rotating LRU list" scheme

CuriousGeorgiy · 2022-09-29T14:41:43Z

src/box/vy_run.c

 */
 static inline void
-vy_page_ref(struct vy_page *page)
+vy_page_ref(struct vy_run *run, struct vy_page_info *page_info)


Guess you should be passing just the page number here.

Looked simplier to me as we often already have page_info in use and there is no need to re-access it via number + run. Anyways, already deleted all the ref-related functions

CuriousGeorgiy · 2022-09-29T14:41:50Z

src/box/vy_run.c

 */
 static inline void
-vy_page_unref(struct vy_page_info *page_info)
+vy_page_unref(struct vy_run *run, struct vy_page_info *page_info)


Guess you should be passing just the page number here.

Looked simplier to me as we often already have page_info in use and there is no need to re-access it via number + run. Anyways, already deleted all the ref-related functions

CuriousGeorgiy · 2022-09-29T14:42:55Z

src/box/vy_run.c

+		assert(tail_page->ri_refs == 0);
+		run->run_env->pc_env.mem_used -= (tail_item->unpacked_size +
+				sizeof(struct vy_page) + tail_item->row_count *
+				sizeof(*tail_page->row_index));


Since you use this in two places, please refactor it out into a separate function.

Done, see the vy_page_cache_account_page_mem() and vy_page_cache_unaccount_page_mem() functions in last commits

CuriousGeorgiy · 2022-09-29T14:44:50Z

src/box/vy_run.c

+{
+	env->mem_quota = 0;		//temp/ looks tricky, but done just as for tuple cache
+	env->mem_used = 0;
+	env->del_percent = 20;		//temp/ literally should be changed at least to a constant


Let's use ratio instead of percentage.

Already abandoned the percentage-based cutbacks and switched to a classic "rotating LRU list" scheme

@TarantoolBot

Every vinyl's run iterator independently keeps 2 uncompressed pages stored in memory - the current one and the previous one used by this exact iterator. 2 most recently requested pages stored for each run iterator do not provide much of caching effect and are used mainly to boost working with multi-page data chunks. So in practice if a tuple is not found in tuple cache, the engine almost always has to read run files. The latter incurs severe overhead even if the pages being read happen to be found in system page cache, because run files are compressed and we have to decompress them on each read. Besides, relying on system page cache eviction algorithm may result in sub-optimal performance. To address this problem, we make vinyl store some amount of unused pages in memory (up to page cache memory quota), giving preference to most recently requested (among all runs) ones. These pages are stored in uncompressed state, so in case of page cache hit no reading from the disk or decompression is required. As an additional effect, by making the way of storing pages in memory suitable for page cache usage, we prevent duplicating pages in memory. Currently, if an iterator receives a request on a page that is already stored in memory but attached to another iterator, it will re-read this page from the disk and decompress it, creating a page's copy. We make run iterators access pages via run-wise centralized metadata structures, so that no more duplicates of existing (in memory) pages are created. Closes tarantool#3202 @TarantoolBot document Title: new box.cfg parameter: 'vinyl_page_cache' `vinyl_page_cache` puts a limit on the amount of RAM that can be occupied by currently unused runs' pages, stored in Vinyl's page cache. The `vinyl_page_cache` limit can be periodically exceeded by up to the approximate size of one page + it's metadata, so that pages are not deleted from the cache after being loaded from the disk but before being processed by the engine and pages are not deleted right before being loaded again upon request. `vinyl_page_cache` parameter can be changed dynamically. If the amount of RAM already being used by the page cache is greater than the new quota, Vinyl will immediately free enough cache's memory to fit it in the new limit. If `vinyl_page_cache` is set to 0, page cache keeps only 1 page in memory (for the entire engine!), so its performance (and the engine's performance as well) drops significantly. Therefore it is strongly recommended not to set `vinyl_page_cache` to 0 if RAM resources are not exhausted.

quaiion changed the title ~~Pull request dedicated to implement vinyl page cache~~ Implement page cache for Vinyl Aug 24, 2022

CuriousGeorgiy assigned CuriousGeorgiy and Korablev77 Aug 24, 2022

CuriousGeorgiy requested review from CuriousGeorgiy and Korablev77 August 24, 2022 11:58

quaiion force-pushed the qn/gh-3202-page-cache-implementation branch from 1718afe to b483d7b Compare September 27, 2022 16:25

CuriousGeorgiy marked this pull request as ready for review September 29, 2022 12:11

CuriousGeorgiy requested changes Sep 29, 2022

View reviewed changes

quaiion force-pushed the qn/gh-3202-page-cache-implementation branch 6 times, most recently from 5b4c590 to b081ba6 Compare October 6, 2022 13:30

quaiion changed the title ~~Implement page cache for Vinyl~~ vinyl: implement page cache Oct 8, 2022

quaiion force-pushed the qn/gh-3202-page-cache-implementation branch 5 times, most recently from c5d33c6 to 019bcd4 Compare February 23, 2023 21:10

quaiion force-pushed the qn/gh-3202-page-cache-implementation branch from 019bcd4 to 25c3055 Compare February 23, 2023 23:48

kyukhin assigned alyapunov Aug 25, 2023

kyukhin marked this pull request as draft August 25, 2023 07:57

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vinyl: implement page cache #7602

vinyl: implement page cache #7602

quaiion commented Aug 24, 2022 •

edited

CuriousGeorgiy Sep 29, 2022

quaiion Sep 30, 2022

CuriousGeorgiy Sep 29, 2022

quaiion Sep 30, 2022

CuriousGeorgiy Sep 29, 2022

quaiion Sep 30, 2022

CuriousGeorgiy Sep 29, 2022

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CuriousGeorgiy Sep 29, 2022

quaiion Oct 4, 2022 •

edited

CuriousGeorgiy Sep 29, 2022

quaiion Oct 4, 2022 •

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CuriousGeorgiy Sep 29, 2022

quaiion Oct 4, 2022

CuriousGeorgiy Sep 29, 2022

quaiion Oct 4, 2022

vinyl: implement page cache #7602

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vinyl: implement page cache #7602

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quaiion commented Aug 24, 2022 • edited

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quaiion Oct 4, 2022 • edited

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quaiion commented Aug 24, 2022 •

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quaiion Oct 4, 2022 •

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quaiion Oct 4, 2022 •

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