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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 4657BC433DB for ; Wed, 10 Feb 2021 02:26:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11E6D64E53 for ; Wed, 10 Feb 2021 02:26:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235260AbhBJCZ4 (ORCPT ); Tue, 9 Feb 2021 21:25:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49440 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234490AbhBJB4m (ORCPT ); Tue, 9 Feb 2021 20:56:42 -0500 Received: from mail-ej1-x632.google.com (mail-ej1-x632.google.com [IPv6:2a00:1450:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 93BF6C061574; Tue, 9 Feb 2021 17:56:00 -0800 (PST) Received: by mail-ej1-x632.google.com with SMTP id hs11so1178422ejc.1; Tue, 09 Feb 2021 17:56:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=iXzyQRaZuZLiOTft75iVeWNV8ABt+eviKyZflZxsDf0=; b=u9N40c8pqBcVi9ZVa541u8zKrGM31TNWTLaGjuuPlHIqKIlniAMMx03F5z1VbsYoiy FwXtnI4Hbt+EzMVF3ER6DN8dGFQBT/bZqQN4RZSrGWFYFTfkVBUSaDSGiAQO+//uAQsL o4XxSPyazRzGjGDHi8CG9kekMyoDbiujY9lBPwA5Ysr0d0LJEn9aqSsc3nbxnvD2jRkA kNDE88N8AkpPJ4ZDkRdHLWhQ28UhezV6SXHSWESE9uD/hhQbPFTbvoknYbBQ2i6AV7Go pXy6iomX5fmp+xE+WJG86XTQMjk+Odjkbb24nWcUuAk/Ta1iJGz+sMuZXfQg7l4eNav/ MYzQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=iXzyQRaZuZLiOTft75iVeWNV8ABt+eviKyZflZxsDf0=; b=LbBC9G78d/1DMMVfwm5olbsy9d1ygk4AzSnLzPyn3VDIxqFFtB8SZwyMu5m2kf98Ii DYXDUmrt8CqABDj+5CKnRZGuxLYW/cJ7iUN+GTCxNnrZhjDs6FUY6N4z6vlh7LmsR4ZA v3IJYoswAuD8Re4MNBTWI87dPVgRuHr+WIVPFM149ndA4EClxJxJFOJ2L4vH4jBWfbDH ZRy+kpG3/aiF6CbAENN+FTiQjnVXod4gsjb5WdmTlmMbtVZGmsmMe7g4roAfafPqBw9h LXHpWazN8qmYV+56Hagph8vxT81DhgbRyuhh4QDhgDK6ol7N7Pd2ZGsLiyMd5UJaQSgG hBqg== X-Gm-Message-State: AOAM531IZ5cDHD/b2eXBd/JrD6BPss7RwZ/iz9WmYfwKF0QoJCk4lisR MwQqeJyf32PoKH+0KTnqgDf3pKQpXySvVIG1vGc= X-Google-Smtp-Source: ABdhPJxoECQS7fASBKCTB+FlHMhofqjM9YkRBKoLEyTGobjb5HQlARul98/mUTVsWv82ITqGiioeJh6PZqP1RsyZlMU= X-Received: by 2002:a17:906:eca5:: with SMTP id qh5mr565421ejb.161.1612922159247; Tue, 09 Feb 2021 17:55:59 -0800 (PST) MIME-Version: 1.0 References: <20210209174646.1310591-1-shy828301@gmail.com> <20210209174646.1310591-8-shy828301@gmail.com> <20210210003943.GK524633@carbon.DHCP.thefacebook.com> <20210210013404.GQ524633@carbon.DHCP.thefacebook.com> In-Reply-To: <20210210013404.GQ524633@carbon.DHCP.thefacebook.com> From: Yang Shi Date: Tue, 9 Feb 2021 17:55:47 -0800 Message-ID: Subject: Re: [v7 PATCH 07/12] mm: vmscan: use a new flag to indicate shrinker is registered To: Roman Gushchin Cc: Kirill Tkhai , Vlastimil Babka , Shakeel Butt , Dave Chinner , Johannes Weiner , Michal Hocko , Andrew Morton , Linux MM , Linux FS-devel Mailing List , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 9, 2021 at 5:34 PM Roman Gushchin wrote: > > On Tue, Feb 09, 2021 at 05:12:51PM -0800, Yang Shi wrote: > > On Tue, Feb 9, 2021 at 4:39 PM Roman Gushchin wrote: > > > > > > On Tue, Feb 09, 2021 at 09:46:41AM -0800, Yang Shi wrote: > > > > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > > > > This approach is fine with nr_deferred at the shrinker level, but the following > > > > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > > > > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > > > > from unregistering correctly. > > > > > > > > Remove SHRINKER_REGISTERING since we could check if shrinker is registered > > > > successfully by the new flag. > > > > > > > > Acked-by: Kirill Tkhai > > > > Signed-off-by: Yang Shi > > > > --- > > > > include/linux/shrinker.h | 7 ++++--- > > > > mm/vmscan.c | 31 +++++++++---------------------- > > > > 2 files changed, 13 insertions(+), 25 deletions(-) > > > > > > > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > > > > index 0f80123650e2..1eac79ce57d4 100644 > > > > --- a/include/linux/shrinker.h > > > > +++ b/include/linux/shrinker.h > > > > @@ -79,13 +79,14 @@ struct shrinker { > > > > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > > > > > > > /* Flags */ > > > > -#define SHRINKER_NUMA_AWARE (1 << 0) > > > > -#define SHRINKER_MEMCG_AWARE (1 << 1) > > > > +#define SHRINKER_REGISTERED (1 << 0) > > > > +#define SHRINKER_NUMA_AWARE (1 << 1) > > > > +#define SHRINKER_MEMCG_AWARE (1 << 2) > > > > /* > > > > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > > > > * non-MEMCG_AWARE shrinker should not have this flag set. > > > > */ > > > > -#define SHRINKER_NONSLAB (1 << 2) > > > > +#define SHRINKER_NONSLAB (1 << 3) > > > > > > > > extern int prealloc_shrinker(struct shrinker *shrinker); > > > > extern void register_shrinker_prepared(struct shrinker *shrinker); > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > > index 273efbf4d53c..a047980536cf 100644 > > > > --- a/mm/vmscan.c > > > > +++ b/mm/vmscan.c > > > > @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) > > > > } > > > > } > > > > > > > > -/* > > > > - * We allow subsystems to populate their shrinker-related > > > > - * LRU lists before register_shrinker_prepared() is called > > > > - * for the shrinker, since we don't want to impose > > > > - * restrictions on their internal registration order. > > > > - * In this case shrink_slab_memcg() may find corresponding > > > > - * bit is set in the shrinkers map. > > > > - * > > > > - * This value is used by the function to detect registering > > > > - * shrinkers and to skip do_shrink_slab() calls for them. > > > > - */ > > > > -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL) > > > > - > > > > static DEFINE_IDR(shrinker_idr); > > > > > > > > static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > > > > > down_write(&shrinker_rwsem); > > > > /* This may call shrinker, so it must use down_read_trylock() */ > > > > - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); > > > > + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); > > > > if (id < 0) > > > > goto unlock; > > > > > > > > @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > > > > { > > > > down_write(&shrinker_rwsem); > > > > list_add_tail(&shrinker->list, &shrinker_list); > > > > -#ifdef CONFIG_MEMCG > > > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > - idr_replace(&shrinker_idr, shrinker, shrinker->id); > > > > -#endif > > > > + shrinker->flags |= SHRINKER_REGISTERED; > > > > up_write(&shrinker_rwsem); > > > > } > > > > > > > > @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker); > > > > */ > > > > void unregister_shrinker(struct shrinker *shrinker) > > > > { > > > > - if (!shrinker->nr_deferred) > > > > + if (!(shrinker->flags & SHRINKER_REGISTERED)) > > > > return; > > > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > - unregister_memcg_shrinker(shrinker); > > > > + > > > > down_write(&shrinker_rwsem); > > > > list_del(&shrinker->list); > > > > + shrinker->flags &= ~SHRINKER_REGISTERED; > > > > up_write(&shrinker_rwsem); > > > > + > > > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > + unregister_memcg_shrinker(shrinker); > > > > > > Because unregister_memcg_shrinker() will take and release shrinker_rwsem once again, > > > I wonder if it's better to move it into the locked section and change the calling > > > convention to require the caller to take the semaphore? > > > > I don't think we could do that since unregister_memcg_shrinker() is > > called by free_prealloced_shrinker() which is called without holding > > the shrinker_rwsem by fs and workingset code. > > > > We could add a bool parameter to indicate if the rwsem was acquired or > > not, but IMHO it seems not worth it. > > Can free_preallocated_shrinker() just do > > if (shrinker->flags & SHRINKER_MEMCG_AWARE) { > down_write(&shrinker_rwsem); > unregister_memcg_shrinker(shrinker); > up_write(&shrinker_rwsem); > } > > ? Aha, yes. I didn't think of that way. 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s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=iXzyQRaZuZLiOTft75iVeWNV8ABt+eviKyZflZxsDf0=; b=nq26BZQXJ2L1keWcJkE2rDpm85cfUIJqYCf5ibjouySsMkRwqrd5QSYUTri9oFPVd3 BkIZc20W6MutuuxVCTASg+Ef95XFp/MN7XXCzqlTF3QePs5jCgDcxEuKBidcpXhvPGJ3 p39jGq/7rZm1hKQxSm2tYNJHwyGQ6NFBSCDpVAwH3OKHPLNtkuVutm3oBC5AXj63gBnh YHJCcU1eCT6lwVBjwyZx29LeSRBMe0RG89hCIf6Bogy530b4+b+skaK6jMULqIrB8McN BnZ3ojDsTaW47G1iDGSPCULGonbUEvZX1/CW29s9pVKtcpuPCdJvKNABwwJ70FszhKPz PMCg== X-Gm-Message-State: AOAM530egUFPqobfqMEHBV53g48WLg7mEU/hyYswCorZdjhw1dSIBLbL 5Tu4g4bKQp0jdSkXCAGUzpZ1G3JvD88NBpCPYIY= X-Google-Smtp-Source: ABdhPJxoECQS7fASBKCTB+FlHMhofqjM9YkRBKoLEyTGobjb5HQlARul98/mUTVsWv82ITqGiioeJh6PZqP1RsyZlMU= X-Received: by 2002:a17:906:eca5:: with SMTP id qh5mr565421ejb.161.1612922159247; Tue, 09 Feb 2021 17:55:59 -0800 (PST) MIME-Version: 1.0 References: <20210209174646.1310591-1-shy828301@gmail.com> <20210209174646.1310591-8-shy828301@gmail.com> <20210210003943.GK524633@carbon.DHCP.thefacebook.com> <20210210013404.GQ524633@carbon.DHCP.thefacebook.com> In-Reply-To: <20210210013404.GQ524633@carbon.DHCP.thefacebook.com> From: Yang Shi Date: Tue, 9 Feb 2021 17:55:47 -0800 Message-ID: Subject: Re: [v7 PATCH 07/12] mm: vmscan: use a new flag to indicate shrinker is registered To: Roman Gushchin Cc: Kirill Tkhai , Vlastimil Babka , Shakeel Butt , Dave Chinner , Johannes Weiner , Michal Hocko , Andrew Morton , Linux MM , Linux FS-devel Mailing List , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" 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: On Tue, Feb 9, 2021 at 5:34 PM Roman Gushchin wrote: > > On Tue, Feb 09, 2021 at 05:12:51PM -0800, Yang Shi wrote: > > On Tue, Feb 9, 2021 at 4:39 PM Roman Gushchin wrote: > > > > > > On Tue, Feb 09, 2021 at 09:46:41AM -0800, Yang Shi wrote: > > > > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > > > > This approach is fine with nr_deferred at the shrinker level, but the following > > > > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > > > > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > > > > from unregistering correctly. > > > > > > > > Remove SHRINKER_REGISTERING since we could check if shrinker is registered > > > > successfully by the new flag. > > > > > > > > Acked-by: Kirill Tkhai > > > > Signed-off-by: Yang Shi > > > > --- > > > > include/linux/shrinker.h | 7 ++++--- > > > > mm/vmscan.c | 31 +++++++++---------------------- > > > > 2 files changed, 13 insertions(+), 25 deletions(-) > > > > > > > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > > > > index 0f80123650e2..1eac79ce57d4 100644 > > > > --- a/include/linux/shrinker.h > > > > +++ b/include/linux/shrinker.h > > > > @@ -79,13 +79,14 @@ struct shrinker { > > > > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > > > > > > > /* Flags */ > > > > -#define SHRINKER_NUMA_AWARE (1 << 0) > > > > -#define SHRINKER_MEMCG_AWARE (1 << 1) > > > > +#define SHRINKER_REGISTERED (1 << 0) > > > > +#define SHRINKER_NUMA_AWARE (1 << 1) > > > > +#define SHRINKER_MEMCG_AWARE (1 << 2) > > > > /* > > > > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > > > > * non-MEMCG_AWARE shrinker should not have this flag set. > > > > */ > > > > -#define SHRINKER_NONSLAB (1 << 2) > > > > +#define SHRINKER_NONSLAB (1 << 3) > > > > > > > > extern int prealloc_shrinker(struct shrinker *shrinker); > > > > extern void register_shrinker_prepared(struct shrinker *shrinker); > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > > > index 273efbf4d53c..a047980536cf 100644 > > > > --- a/mm/vmscan.c > > > > +++ b/mm/vmscan.c > > > > @@ -315,19 +315,6 @@ void set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id) > > > > } > > > > } > > > > > > > > -/* > > > > - * We allow subsystems to populate their shrinker-related > > > > - * LRU lists before register_shrinker_prepared() is called > > > > - * for the shrinker, since we don't want to impose > > > > - * restrictions on their internal registration order. > > > > - * In this case shrink_slab_memcg() may find corresponding > > > > - * bit is set in the shrinkers map. > > > > - * > > > > - * This value is used by the function to detect registering > > > > - * shrinkers and to skip do_shrink_slab() calls for them. > > > > - */ > > > > -#define SHRINKER_REGISTERING ((struct shrinker *)~0UL) > > > > - > > > > static DEFINE_IDR(shrinker_idr); > > > > > > > > static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > @@ -336,7 +323,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > > > > > > > > down_write(&shrinker_rwsem); > > > > /* This may call shrinker, so it must use down_read_trylock() */ > > > > - id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); > > > > + id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); > > > > if (id < 0) > > > > goto unlock; > > > > > > > > @@ -499,10 +486,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > > > > { > > > > down_write(&shrinker_rwsem); > > > > list_add_tail(&shrinker->list, &shrinker_list); > > > > -#ifdef CONFIG_MEMCG > > > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > - idr_replace(&shrinker_idr, shrinker, shrinker->id); > > > > -#endif > > > > + shrinker->flags |= SHRINKER_REGISTERED; > > > > up_write(&shrinker_rwsem); > > > > } > > > > > > > > @@ -522,13 +506,16 @@ EXPORT_SYMBOL(register_shrinker); > > > > */ > > > > void unregister_shrinker(struct shrinker *shrinker) > > > > { > > > > - if (!shrinker->nr_deferred) > > > > + if (!(shrinker->flags & SHRINKER_REGISTERED)) > > > > return; > > > > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > - unregister_memcg_shrinker(shrinker); > > > > + > > > > down_write(&shrinker_rwsem); > > > > list_del(&shrinker->list); > > > > + shrinker->flags &= ~SHRINKER_REGISTERED; > > > > up_write(&shrinker_rwsem); > > > > + > > > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > > > > + unregister_memcg_shrinker(shrinker); > > > > > > Because unregister_memcg_shrinker() will take and release shrinker_rwsem once again, > > > I wonder if it's better to move it into the locked section and change the calling > > > convention to require the caller to take the semaphore? > > > > I don't think we could do that since unregister_memcg_shrinker() is > > called by free_prealloced_shrinker() which is called without holding > > the shrinker_rwsem by fs and workingset code. > > > > We could add a bool parameter to indicate if the rwsem was acquired or > > not, but IMHO it seems not worth it. > > Can free_preallocated_shrinker() just do > > if (shrinker->flags & SHRINKER_MEMCG_AWARE) { > down_write(&shrinker_rwsem); > unregister_memcg_shrinker(shrinker); > up_write(&shrinker_rwsem); > } > > ? Aha, yes. I didn't think of that way.