Messages in this thread | | | From | Andy Whitcroft <> | Subject | [PATCH 0/4] Reclaim page capture v3 | Date | Fri, 5 Sep 2008 11:19:58 +0100 |
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For sometime we have been looking at mechanisms for improving the availability of larger allocations under load. One of the options we have explored is the capturing of pages freed under direct reclaim in order to increase the chances of free pages coelescing before they are subject to reallocation by racing allocators.
Following this email is a patch stack implementing page capture during direct reclaim. It consits of four patches. The first two simply pull out existing code into helpers for reuse. The third makes buddy's use of struct page explicit. The fourth contains the meat of the changes, and its leader contains a much fuller description of the feature.
This update represents a rebase to -mm and incorporates feedback from KOSAKI Motohiro. It also incorporates an accounting fix which was preventing some captures.
I have done a lot of comparitive testing with and without this patch set and in broad brush I am seeing improvements in hugepage allocations (worst case size) success on all of my test systems. These tests consist of placing a constant stream of high order allocations on the system, at varying rates. The results for these various runs are then averaged to give an overall improvement.
Absolute Effective x86-64 2.48% 4.58% powerpc 5.55% 25.22%
x86-64 has a relatively small huge page size and so is always much more effective at allocating huge pages. Even there we get a measurable improvement. On powerpc the huge pages are much larger and much harder to recover. Here we see a full 25% increase in page recovery.
It should be noted that these are worst case testing, and very agressive taking every possible page in the system. It would be helpful to get wider testing in -mm.
Against: 2.6.27-rc1-mm1
Andrew, please consider for -mm.
-apw
Changes since V2: - Incorporates review feedback from Christoph Lameter, - Incorporates review feedback from Peter Zijlstra, and - Checkpatch fixes.
Changes since V1: - Incorporates review feedback from KOSAKI Motohiro, - fixes up accounting when checking watermarks for captured pages, - rebase 2.6.27-rc1-mm1, - Incorporates review feedback from Mel.
Andy Whitcroft (4): pull out the page pre-release and sanity check logic for reuse pull out zone cpuset and watermark checks for reuse buddy: explicitly identify buddy field use in struct page capture pages freed during direct reclaim for allocation by the reclaimer
include/linux/mm_types.h | 4 + include/linux/page-flags.h | 4 + mm/internal.h | 8 +- mm/page_alloc.c | 263 ++++++++++++++++++++++++++++++++++++++------ mm/vmscan.c | 115 ++++++++++++++++---- 5 files changed, 338 insertions(+), 56 deletions(-)
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