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[209.85.220.65]) by mx.google.com with SMTPS id p61sor20455130plb.47.2019.06.19.01.08.39 for (Google Transport Security); Wed, 19 Jun 2019 01:08:39 -0700 (PDT) Received-SPF: pass (google.com: domain of vovoy@chromium.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@chromium.org header.s=google header.b=U6WZCxft; spf=pass (google.com: domain of vovoy@chromium.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=vovoy@chromium.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=chromium.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=hDeVdBWWPPTkbBXHklX8Rt51hyYEzQf0jmQ1XrF86ag=; b=U6WZCxft1YmIyjwH5Znr6VX8IS/f71mPVNA/6CormE/HP80HaNHImYH+aM1yKclQRS KCCZkUoz8mjPWW++D5Z9ltxghClm58t9I54NwSBZ8Tuv7YxrBqdbm8nkyUG5CuHaGJkZ PFhFI26MFip3NWmg15ii8LdoQVSa3a2dWvRdY= X-Google-Smtp-Source: APXvYqy0Rhm4TA+2ZMv3rfgXXv14ZYAZHjJV4QK7rYCsewfrnKIbNiKGk15ogGJUnV+a1ciO9lI0vA== X-Received: by 2002:a17:902:903:: with SMTP id 3mr93535586plm.281.1560931718751; Wed, 19 Jun 2019 01:08:38 -0700 (PDT) Received: from google.com ([2401:fa00:1:b:d89e:cfa6:3c8:e61b]) by smtp.gmail.com with ESMTPSA id c26sm740179pfr.172.2019.06.19.01.08.37 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 19 Jun 2019 01:08:38 -0700 (PDT) Date: Wed, 19 Jun 2019 16:08:35 +0800 From: Kuo-Hsin Yang To: Andrew Morton , Johannes Weiner Cc: Michal Hocko , Sonny Rao , Kuo-Hsin Yang , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] mm: vmscan: fix not scanning anonymous pages when detecting file refaults Message-ID: <20190619080835.GA68312@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: When file refaults are detected and there are many inactive file pages, the system never reclaim anonymous pages, the file pages are dropped aggressively when there are still a lot of cold anonymous pages and system thrashes. This issue impacts the performance of applications with large executable, e.g. chrome. When file refaults are detected. inactive_list_is_low() may return different values depends on the actual_reclaim parameter, the following 2 conditions could be satisfied at the same time. 1) inactive_list_is_low() returns false in get_scan_count() to trigger scanning file lists only. 2) inactive_list_is_low() returns true in shrink_list() to allow scanning active file list. In that case vmscan would only scan file lists, and as active file list is also scanned, inactive_list_is_low() may keep returning false in get_scan_count() until file cache is very low. Before commit 2a2e48854d70 ("mm: vmscan: fix IO/refault regression in cache workingset transition"), inactive_list_is_low() never returns different value in get_scan_count() and shrink_list() in one shrink_node_memcg() run. The original design should be that when inactive_list_is_low() returns false for file lists, vmscan only scan inactive file list. As only inactive file list is scanned, inactive_list_is_low() would soon return true. This patch makes the return value of inactive_list_is_low() independent of actual_reclaim. The problem can be reproduced by the following test program. ---8<--- void fallocate_file(const char *filename, off_t size) { struct stat st; int fd; if (!stat(filename, &st) && st.st_size >= size) return; fd = open(filename, O_WRONLY | O_CREAT, 0600); if (fd < 0) { perror("create file"); exit(1); } if (posix_fallocate(fd, 0, size)) { perror("fallocate"); exit(1); } close(fd); } long *alloc_anon(long size) { long *start = malloc(size); memset(start, 1, size); return start; } long access_file(const char *filename, long size, long rounds) { int fd, i; volatile char *start1, *end1, *start2; const int page_size = getpagesize(); long sum = 0; fd = open(filename, O_RDONLY); if (fd == -1) { perror("open"); exit(1); } /* * Some applications, e.g. chrome, use a lot of executable file * pages, map some of the pages with PROT_EXEC flag to simulate * the behavior. */ start1 = mmap(NULL, size / 2, PROT_READ | PROT_EXEC, MAP_SHARED, fd, 0); if (start1 == MAP_FAILED) { perror("mmap"); exit(1); } end1 = start1 + size / 2; start2 = mmap(NULL, size / 2, PROT_READ, MAP_SHARED, fd, size / 2); if (start2 == MAP_FAILED) { perror("mmap"); exit(1); } for (i = 0; i < rounds; ++i) { struct timeval before, after; volatile char *ptr1 = start1, *ptr2 = start2; gettimeofday(&before, NULL); for (; ptr1 < end1; ptr1 += page_size, ptr2 += page_size) sum += *ptr1 + *ptr2; gettimeofday(&after, NULL); printf("File access time, round %d: %f (sec)\n", i, (after.tv_sec - before.tv_sec) + (after.tv_usec - before.tv_usec) / 1000000.0); } return sum; } int main(int argc, char *argv[]) { const long MB = 1024 * 1024; long anon_mb, file_mb, file_rounds; const char filename[] = "large"; long *ret1; long ret2; if (argc != 4) { printf("usage: thrash ANON_MB FILE_MB FILE_ROUNDS\n"); exit(0); } anon_mb = atoi(argv[1]); file_mb = atoi(argv[2]); file_rounds = atoi(argv[3]); fallocate_file(filename, file_mb * MB); printf("Allocate %ld MB anonymous pages\n", anon_mb); ret1 = alloc_anon(anon_mb * MB); printf("Access %ld MB file pages\n", file_mb); ret2 = access_file(filename, file_mb * MB, file_rounds); printf("Print result to prevent optimization: %ld\n", *ret1 + ret2); return 0; } ---8<--- Running the test program on 2GB RAM VM with kernel 5.2.0-rc5, the program fills ram with 2048 MB memory, access a 200 MB file for 10 times. Without this patch, the file cache is dropped aggresively and every access to the file is from disk. $ ./thrash 2048 200 10 Allocate 2048 MB anonymous pages Access 200 MB file pages File access time, round 0: 2.489316 (sec) File access time, round 1: 2.581277 (sec) File access time, round 2: 2.487624 (sec) File access time, round 3: 2.449100 (sec) File access time, round 4: 2.420423 (sec) File access time, round 5: 2.343411 (sec) File access time, round 6: 2.454833 (sec) File access time, round 7: 2.483398 (sec) File access time, round 8: 2.572701 (sec) File access time, round 9: 2.493014 (sec) With this patch, these file pages can be cached. $ ./thrash 2048 200 10 Allocate 2048 MB anonymous pages Access 200 MB file pages File access time, round 0: 2.475189 (sec) File access time, round 1: 2.440777 (sec) File access time, round 2: 2.411671 (sec) File access time, round 3: 1.955267 (sec) File access time, round 4: 0.029924 (sec) File access time, round 5: 0.000808 (sec) File access time, round 6: 0.000771 (sec) File access time, round 7: 0.000746 (sec) File access time, round 8: 0.000738 (sec) File access time, round 9: 0.000747 (sec) Fixes: 2a2e48854d70 ("mm: vmscan: fix IO/refault regression in cache workingset transition") Signed-off-by: Kuo-Hsin Yang --- mm/vmscan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 7889f583ced9f..b95d05fe828d1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2151,7 +2151,7 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file, * rid of the stale workingset quickly. */ refaults = lruvec_page_state_local(lruvec, WORKINGSET_ACTIVATE); - if (file && actual_reclaim && lruvec->refaults != refaults) { + if (file && lruvec->refaults != refaults) { inactive_ratio = 0; } else { gb = (inactive + active) >> (30 - PAGE_SHIFT); -- 2.22.0.410.gd8fdbe21b5-goog