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 C583EC433DB for ; Wed, 10 Feb 2021 01:15:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E05764E3B for ; Wed, 10 Feb 2021 01:15:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233571AbhBJBPR (ORCPT ); Tue, 9 Feb 2021 20:15:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40286 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234763AbhBJBNo (ORCPT ); Tue, 9 Feb 2021 20:13:44 -0500 Received: from mail-ej1-x636.google.com (mail-ej1-x636.google.com [IPv6:2a00:1450:4864:20::636]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D086C061574; Tue, 9 Feb 2021 17:13:04 -0800 (PST) Received: by mail-ej1-x636.google.com with SMTP id i8so970609ejc.7; Tue, 09 Feb 2021 17:13:04 -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=5NyVpcKF9IDJOlvqTT3/NHGSaLgusSzNFcBiCjC++Xk=; b=Jsi4eD4g8f/QE/oCmAZsem7AxqzyIZQJc51NfsnXl2wpUTQeQOJFAaM9pzcQ8ABUxL UVH9e/4Sl26vu2vRD3PixHniJ+9QdUqhX2YHnuMRwv8KWYfhbPc2wUh5qKHTockiebjy cdx7icfst5jHw+Ne3kyptnYNL5ZigC8QHrCZpLY6APS8F4w7kjGDW9QZiOqi2etu8ALS RUiZdfSG+BruveE8wc9tDlFevLTGiJ1+7hNu8Cm5ujAeRm8MGQi9jMH7Bm4mw3XlUepL KeF+cJdunFSYGD4uuhAbvzBWZU9CZaGzGmlWi8u9PMAyKxbAL+WNBumwO1qBkU4FDFF1 3UMg== 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=5NyVpcKF9IDJOlvqTT3/NHGSaLgusSzNFcBiCjC++Xk=; b=H6kACDnun5+9vXE7xzfr/qBbB+Is97iqGXTbvakzuaer1u8qHC/67hmDCVD+nWtDMn v+qcXZuN9xHPwPSbnu5QQyqNl7E3eMH7qp74Ig36zafvIWg1teXLH6r2X1Tornlzv2rf 28x+hleSBE8D9XK+mE7S5WWH29OPOWxG0H3Yznpa6zARFwmhGcLR880hd3vVrkn0u7nI wR6rwmWgTKnGW1vMeNTynXZVIOh7XYoGj5p6/GhCHrzNr7aK1MIhbpPTOOhPgZ8Qai6r S5f9WF0P5Swl/4/MspJf6iR5LtGiukOPuCLsLnDTgi06befVuNtPcdVBRH6XVEu02K2R ADbg== X-Gm-Message-State: AOAM530HUn/8zF73J5BHI82kvx3YCef3W4GAxO+LWu9czCa6YAafwhQE wLTosuE/9vocFlb3l7dGkA7hImyl44wiFHFl31DWX2lARRE= X-Google-Smtp-Source: ABdhPJyTWutKg/k2AEX+z3Y966q4sikpTAQVazuE+L9ySrzGkceIVyL2ltn6UlSwcmWSiHhR6gSRkmfiSfip9KkACbM= X-Received: by 2002:a17:906:eca5:: with SMTP id qh5mr429264ejb.161.1612919583218; Tue, 09 Feb 2021 17:13:03 -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> In-Reply-To: <20210210003943.GK524633@carbon.DHCP.thefacebook.com> From: Yang Shi Date: Tue, 9 Feb 2021 17:12:51 -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-fsdevel@vger.kernel.org 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. > > > kfree(shrinkrem->nr_deferred); > > shrinker->nr_deferred = NULL; > > } > > @@ -693,7 +680,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, > > struct shrinker *shrinker; > > > > shrinker = idr_find(&shrinker_idr, i); > > - if (unlikely(!shrinker || shrinker == SHRINKER_REGISTERING)) { > > + if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) { > > if (!shrinker) > > clear_bit(i, info->map); > > continue; > > -- > > 2.26.2 > >