On 2014/6/16 18:04, Zhang Yanfei wrote: > Hi, > > On 06/16/2014 05:24 PM, Xishi Qiu wrote: >> When system(e.g. smart phone) running for a long time, the cache often takes >> a large memory, maybe the free memory is less than 50M, then OOM will happen >> if APP allocate a large order pages suddenly and memory reclaim too slowly. > > If there is really too many page caches, and the free memory is low. I think > the page allocator will enter the slowpath to free more memory for allocation. > And it the slowpath, there is indeed the direct reclaim operation, so is that > really not enough to reclaim pagecaches? > Hi Yanfei, Do you mean this path? __alloc_pages_slowpath() __alloc_pages_direct_reclaim() __perform_reclaim() try_to_free_pages() the "nr_to_reclaim = SWAP_CLUSTER_MAX" is only 32 pages. >> >> Use "echo 3 > /proc/sys/vm/drop_caches" will drop the whole cache, this will >> affect the performance, so it is used for debugging only. >> >> suse has this feature, I tested it before, but it can not limit the page cache >> actually. So I rewrite the feature and add some parameters. >> >> Christoph Lameter has written a patch "Limit the size of the pagecache" >> http://marc.info/?l=linux-mm&m=116959990228182&w=2 >> It changes in zone fallback, this is not a good way. >> >> The patchset is based on v3.15, it introduces two features, page cache limit >> and page cache reclaim in circles. >> >> Add four parameters in /proc/sys/vm >> >> 1) cache_limit_mbytes >> This is used to limit page cache amount. >> The input unit is MB, value range is from 0 to totalram_pages. >> If this is set to 0, it will not limit page cache. >> When written to the file, cache_limit_ratio will be updated too. >> The default value is 0. >> >> 2) cache_limit_ratio >> This is used to limit page cache amount. >> The input unit is percent, value range is from 0 to 100. >> If this is set to 0, it will not limit page cache. >> When written to the file, cache_limit_mbytes will be updated too. >> The default value is 0. >> >> 3) cache_reclaim_s >> This is used to reclaim page cache in circles. >> The input unit is second, the minimum value is 0. >> If this is set to 0, it will disable the feature. >> The default value is 0. >> >> 4) cache_reclaim_weight >> This is used to speed up page cache reclaim. >> It depend on enabling cache_limit_mbytes/cache_limit_ratio or cache_reclaim_s. >> Value range is from 1(slow) to 100(fast). >> The default value is 1. >> >> I tested the two features on my system(x86_64), it seems to work right. >> However, as it changes the hot path "add_to_page_cache_lru()", I don't know >> how much it will the affect the performance, > > Yeah, at a quick glance, for every invoke of add_to_page_cache_lru(), there is the > newly added test: > > if (vm_cache_limit_mbytes && page_cache_over_limit()) > > and if the test is passed, shrink_page_cache()->do_try_to_free_pages() is called. > And this is a sync operation. IMO, it is better to make such an operation async. > (You've implemented async operation but I doubt if it is suitable to put the sync operation > here.) > > Thanks. > Sounds to a good idea, how about waking up kswapd()? Thanks, Xishi Qiu > maybe there are some errors >> in the patches too, RFC. >> >> >> *** BLURB HERE *** >> >> Xishi Qiu (8): >> mm: introduce cache_limit_ratio and cache_limit_mbytes >> mm: add shrink page cache core >> mm: implement page cache limit feature >> mm: introduce cache_reclaim_s >> mm: implement page cache reclaim in circles >> mm: introduce cache_reclaim_weight >> mm: implement page cache reclaim speed >> doc: update Documentation/sysctl/vm.txt >> >> Documentation/sysctl/vm.txt | 43 +++++++++++++++++++ >> include/linux/swap.h | 17 ++++++++ >> kernel/sysctl.c | 35 +++++++++++++++ >> mm/filemap.c | 3 + >> mm/hugetlb.c | 3 + >> mm/page_alloc.c | 51 ++++++++++++++++++++++ >> mm/vmscan.c | 97 ++++++++++++++++++++++++++++++++++++++++++- >> 7 files changed, 248 insertions(+), 1 deletions(-) >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >> . >> > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>