From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34544C43218 for ; Tue, 11 Jun 2019 12:29:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E8E592089E for ; Tue, 11 Jun 2019 12:29:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="q44jIWre" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729316AbfFKM3z (ORCPT ); Tue, 11 Jun 2019 08:29:55 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:41206 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727278AbfFKM3y (ORCPT ); Tue, 11 Jun 2019 08:29:54 -0400 Received: by mail-pf1-f194.google.com with SMTP id m30so6839028pff.8 for ; Tue, 11 Jun 2019 05:29:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=y7gj05j+fTkifIRrdspgMrrd6G03saWrwNWynfBgS0U=; b=q44jIWreO5gdxzKinRevyVBXJSZQf8U+XKtuF2X+lzP726yGNOhXZCwF57PB5EMk2+ 3glGSCjLduh3nhIIVEzbXq/3LxETJr0vwhLBFpXPg1uM6vpyd9iR6/JFPDsXKB1H0g+W FoBB88T3IZZrFcKKcrwIoYX7D9lToHjdaWGEXFfmd9FxK69PRvptwMSUl3rdYgG+Kvoi O5oZlBdovnhg3TuqK6vS/1QVpw8QUgTpGAFVCutWvhjkRHiRSn8uARrmFM/5opytIhtt IlNBfi0I1q4bDDpZkAMPY1x2fWQzNTPwIKyM+rLYyeZal96gQSvR+viOZ1me5cB6P24F TEGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=y7gj05j+fTkifIRrdspgMrrd6G03saWrwNWynfBgS0U=; b=BqHPu3TuqvD9tBjNHttW+Ltu5SL3zgujjaMlFXX+iDyOW1pc9onlh3lG1ox3ZvTwL6 6w8TRI0K92JBgKap3Wd14xA6biORajAq4Hgu19Rc4pq0+pXyXK0lCLtaC7K5h3JIJxAr UP7oasxOS8uOKcxl3QU8lW2wk/yARDulKaPaWaMhBSotgxlbgYUZo/sHasBNPji1wHoQ Wdf4GaN17rKsgbDUDMZVBR/Y0685mlIlIAcEj77ozOtkg43zcBQ4BOLeuB7DB9atFSOc bibfrVzDUrUP4NCzjWxi+FX+NMrTFWG9bnVU2e8ol5QSH/eE/HejnEigSx91AdZYdpuD Y7Rg== X-Gm-Message-State: APjAAAXQ+QRXZl0BVCEqF31F02q3W3G5Luxdfh7kXXuGr7CNzYAEzyST ESaSZix5uuSEC0ERDVAB+fNpnDk= X-Google-Smtp-Source: APXvYqxZv5u+6uxczWx/QpkRi7je6l/4vwiWO4NDGzDjaiGi1t7F3+s06xKpxFhSxyYobjjdIv03zQ== X-Received: by 2002:a62:fb18:: with SMTP id x24mr79552145pfm.76.1560256193724; Tue, 11 Jun 2019 05:29:53 -0700 (PDT) Received: from dhcp-128-55.nay.redhat.com ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id 24sm13723109pgn.32.2019.06.11.05.29.49 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 11 Jun 2019 05:29:52 -0700 (PDT) Date: Tue, 11 Jun 2019 20:29:35 +0800 From: Pingfan Liu To: John Hubbard Cc: Andrew Morton , linux-mm@kvack.org, Ira Weiny , Mike Rapoport , Dan Williams , Matthew Wilcox , "Aneesh Kumar K.V" , Keith Busch , Christoph Hellwig , LKML Subject: Re: [PATCHv3 1/2] mm/gup: fix omission of check on FOLL_LONGTERM in get_user_pages_fast() Message-ID: <20190611122935.GA9919@dhcp-128-55.nay.redhat.com> References: <1559725820-26138-1-git-send-email-kernelfans@gmail.com> <20190605144912.f0059d4bd13c563ddb37877e@linux-foundation.org> <2b0a65ec-4fb0-430e-3e6a-b713fb5bb28f@nvidia.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="W/nzBZO5zC0uMSeA" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --W/nzBZO5zC0uMSeA Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Jun 07, 2019 at 02:10:15PM +0800, Pingfan Liu wrote: > On Fri, Jun 7, 2019 at 5:17 AM John Hubbard wrote: > > > > On 6/5/19 7:19 PM, Pingfan Liu wrote: > > > On Thu, Jun 6, 2019 at 5:49 AM Andrew Morton wrote: > > ... > > >>> --- a/mm/gup.c > > >>> +++ b/mm/gup.c > > >>> @@ -2196,6 +2196,26 @@ static int __gup_longterm_unlocked(unsigned long start, int nr_pages, > > >>> return ret; > > >>> } > > >>> > > >>> +#ifdef CONFIG_CMA > > >>> +static inline int reject_cma_pages(int nr_pinned, struct page **pages) > > >>> +{ > > >>> + int i; > > >>> + > > >>> + for (i = 0; i < nr_pinned; i++) > > >>> + if (is_migrate_cma_page(pages[i])) { > > >>> + put_user_pages(pages + i, nr_pinned - i); > > >>> + return i; > > >>> + } > > >>> + > > >>> + return nr_pinned; > > >>> +} > > >> > > >> There's no point in inlining this. > > > OK, will drop it in V4. > > > > > >> > > >> The code seems inefficient. If it encounters a single CMA page it can > > >> end up discarding a possibly significant number of non-CMA pages. I > > > The trick is the page is not be discarded, in fact, they are still be > > > referrenced by pte. We just leave the slow path to pick up the non-CMA > > > pages again. > > > > > >> guess that doesn't matter much, as get_user_pages(FOLL_LONGTERM) is > > >> rare. But could we avoid this (and the second pass across pages[]) by > > >> checking for a CMA page within gup_pte_range()? > > > It will spread the same logic to hugetlb pte and normal pte. And no > > > improvement in performance due to slow path. So I think maybe it is > > > not worth. > > > > > >> > > > > I think the concern is: for the successful gup_fast case with no CMA > > pages, this patch is adding another complete loop through all the > > pages. In the fast case. > > > > If the check were instead done as part of the gup_pte_range(), then > > it would be a little more efficient for that case. > > > > As for whether it's worth it, *probably* this is too small an effect to measure. > > But in order to attempt a measurement: running fio (https://github.com/axboe/fio) > > with O_DIRECT on an NVMe drive, might shed some light. Here's an fio.conf file > > that Jan Kara and Tom Talpey helped me come up with, for related testing: > > > > [reader] > > direct=1 > > ioengine=libaio > > blocksize=4096 > > size=1g > > numjobs=1 > > rw=read > > iodepth=64 > > Unable to get a NVME device to have a test. And when testing fio on the tranditional disk, I got the error "fio: engine libaio not loadable fio: failed to load engine fio: file:ioengines.c:89, func=dlopen, error=libaio: cannot open shared object file: No such file or directory" But I found a test case which can be slightly adjusted to met the aim. It is tools/testing/selftests/vm/gup_benchmark.c Test enviroment: MemTotal: 264079324 kB MemFree: 262306788 kB CmaTotal: 0 kB CmaFree: 0 kB on AMD EPYC 7601 Test command: gup_benchmark -r 100 -n 64 gup_benchmark -r 100 -n 64 -l where -r stands for repeat times, -n is nr_pages param for get_user_pages_fast(), -l is a new option to test FOLL_LONGTERM in fast path, see a patch at the tail. Test result: w/o 477.800000 w/o-l 481.070000 a 481.800000 a-l 640.410000 b 466.240000 (question a: b outperforms w/o ?) b-l 529.740000 Where w/o is baseline without any patch using v5.2-rc2, a is this series, b does the check in gup_pte_range(). '-l' means FOLL_LONGTERM. I am suprised that b-l has about 17% improvement than a. (640.41 -529.74)/640.41 As for "question a: b outperforms w/o ?", I can not figure out why, maybe it can be considered as variance. Based on the above result, I think it is better to do the check inside gup_pte_range(). Any comment? Thanks, > Yeah, agreed. Data is more persuasive. Thanks for your suggestion. I > will try to bring out the result. > > Thanks, > Pingfan > --W/nzBZO5zC0uMSeA Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="gup_pte_range_check.patch" --- Patch to do check inside gup_pte_range() diff --git a/mm/gup.c b/mm/gup.c index 2ce3091..ba213a0 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1757,6 +1757,10 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); + if (unlikely(flags & FOLL_LONGTERM) && + is_migrate_cma_page(page)) + goto pte_unmap; + head = try_get_compound_head(page, 1); if (!head) goto pte_unmap; @@ -1900,6 +1904,12 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + if (unlikely(flags & FOLL_LONGTERM) && + is_migrate_cma_page(page)) { + *nr -= refs; + return 0; + } + head = try_get_compound_head(pmd_page(orig), refs); if (!head) { *nr -= refs; @@ -1941,6 +1951,12 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + if (unlikely(flags & FOLL_LONGTERM) && + is_migrate_cma_page(page)) { + *nr -= refs; + return 0; + } + head = try_get_compound_head(pud_page(orig), refs); if (!head) { *nr -= refs; @@ -1978,6 +1994,12 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + if (unlikely(flags & FOLL_LONGTERM) && + is_migrate_cma_page(page)) { + *nr -= refs; + return 0; + } + head = try_get_compound_head(pgd_page(orig), refs); if (!head) { *nr -= refs; --W/nzBZO5zC0uMSeA Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="mm-gup-introduce-LONGTERM_BENCHMARK-in-fast-path.patch" --- Patch for testing diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c index 7dd602d..61dec5f 100644 --- a/mm/gup_benchmark.c +++ b/mm/gup_benchmark.c @@ -6,8 +6,9 @@ #include #define GUP_FAST_BENCHMARK _IOWR('g', 1, struct gup_benchmark) -#define GUP_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark) -#define GUP_BENCHMARK _IOWR('g', 3, struct gup_benchmark) +#define GUP_FAST_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark) +#define GUP_LONGTERM_BENCHMARK _IOWR('g', 3, struct gup_benchmark) +#define GUP_BENCHMARK _IOWR('g', 4, struct gup_benchmark) struct gup_benchmark { __u64 get_delta_usec; @@ -53,6 +54,11 @@ static int __gup_benchmark_ioctl(unsigned int cmd, nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i); break; + case GUP_FAST_LONGTERM_BENCHMARK: + nr = get_user_pages_fast(addr, nr, + (gup->flags & 1) | FOLL_LONGTERM, + pages + i); + break; case GUP_LONGTERM_BENCHMARK: nr = get_user_pages(addr, nr, (gup->flags & 1) | FOLL_LONGTERM, @@ -96,6 +102,7 @@ static long gup_benchmark_ioctl(struct file *filep, unsigned int cmd, switch (cmd) { case GUP_FAST_BENCHMARK: + case GUP_FAST_LONGTERM_BENCHMARK: case GUP_LONGTERM_BENCHMARK: case GUP_BENCHMARK: break; diff --git a/tools/testing/selftests/vm/gup_benchmark.c b/tools/testing/selftests/vm/gup_benchmark.c index c0534e2..ade8acb 100644 --- a/tools/testing/selftests/vm/gup_benchmark.c +++ b/tools/testing/selftests/vm/gup_benchmark.c @@ -15,8 +15,9 @@ #define PAGE_SIZE sysconf(_SC_PAGESIZE) #define GUP_FAST_BENCHMARK _IOWR('g', 1, struct gup_benchmark) -#define GUP_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark) -#define GUP_BENCHMARK _IOWR('g', 3, struct gup_benchmark) +#define GUP_FAST_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark) +#define GUP_LONGTERM_BENCHMARK _IOWR('g', 3, struct gup_benchmark) +#define GUP_BENCHMARK _IOWR('g', 4, struct gup_benchmark) struct gup_benchmark { __u64 get_delta_usec; @@ -37,7 +38,7 @@ int main(int argc, char **argv) char *file = "/dev/zero"; char *p; - while ((opt = getopt(argc, argv, "m:r:n:f:tTLUSH")) != -1) { + while ((opt = getopt(argc, argv, "m:r:n:f:tTlLUSH")) != -1) { switch (opt) { case 'm': size = atoi(optarg) * MB; @@ -54,6 +55,9 @@ int main(int argc, char **argv) case 'T': thp = 0; break; + case 'l': + cmd = GUP_FAST_LONGTERM_BENCHMARK; + break; case 'L': cmd = GUP_LONGTERM_BENCHMARK; break; -- 2.7.5 --W/nzBZO5zC0uMSeA--