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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 E22D5C433B4 for ; Fri, 9 Apr 2021 11:00:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6848610D1 for ; Fri, 9 Apr 2021 11:00:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233773AbhDILAg (ORCPT ); Fri, 9 Apr 2021 07:00:36 -0400 Received: from mx2.suse.de ([195.135.220.15]:34272 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233670AbhDILAg (ORCPT ); Fri, 9 Apr 2021 07:00:36 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9B536B147; Fri, 9 Apr 2021 11:00:22 +0000 (UTC) Subject: Re: [PATCH 1/2] mm/vmscan: add sync_shrinkers function To: =?UTF-8?Q?Christian_K=c3=b6nig?= , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: ray.huang@amd.com, daniel@ffwll.ch, akpm@linux-foundation.org References: <20210409071725.1532-1-christian.koenig@amd.com> From: Vlastimil Babka Message-ID: <462c2a51-4aa8-47ba-1c67-171ca651b016@suse.cz> Date: Fri, 9 Apr 2021 13:00:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210409071725.1532-1-christian.koenig@amd.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/9/21 9:17 AM, Christian König wrote: > To be able to switch to a spinlock and reduce lock contention in the TTM > shrinker we don't want to hold a mutex while unmapping and freeing pages > from the pool. Does using spinlock instead of mutex really reduce lock contention? > But then we somehow need to prevent a race between (for example) the shrinker > trying to free pages and hotplug trying to remove the device which those pages > belong to. > > Taking and releasing the shrinker semaphore on the write side after > unmapping and freeing all pages should make sure that no shrinker is running in > paralell any more. So you explain this in this commit log for adding the function, but then the next patch just adds a sync_shrinkers() call without any comment. I would expect there a comment explaining why it's done there - what it protects against, as it's not an obvious pattern IMHO. > Signed-off-by: Christian König > --- > include/linux/shrinker.h | 1 + > mm/vmscan.c | 10 ++++++++++ > 2 files changed, 11 insertions(+) > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > index 0f80123650e2..6b75dc372fce 100644 > --- a/include/linux/shrinker.h > +++ b/include/linux/shrinker.h > @@ -92,4 +92,5 @@ extern void register_shrinker_prepared(struct shrinker *shrinker); > extern int register_shrinker(struct shrinker *shrinker); > extern void unregister_shrinker(struct shrinker *shrinker); > extern void free_prealloced_shrinker(struct shrinker *shrinker); > +extern void sync_shrinkers(void); > #endif > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 562e87cbd7a1..46cd9c215d73 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -408,6 +408,16 @@ void unregister_shrinker(struct shrinker *shrinker) > } > EXPORT_SYMBOL(unregister_shrinker); > > +/** > + * sync_shrinker - Wait for all running shrinkers to complete. > + */ > +void sync_shrinkers(void) > +{ > + down_write(&shrinker_rwsem); > + up_write(&shrinker_rwsem); > +} > +EXPORT_SYMBOL(sync_shrinkers); > + > #define SHRINK_BATCH 128 > > static unsigned long do_shrink_slab(struct shrink_control *shrinkctl, > 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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 66315C433ED for ; Fri, 9 Apr 2021 11:00:26 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1FAE9610D0 for ; Fri, 9 Apr 2021 11:00:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1FAE9610D0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7CF6B6E491; Fri, 9 Apr 2021 11:00:25 +0000 (UTC) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id 18CD66E491 for ; Fri, 9 Apr 2021 11:00:24 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9B536B147; Fri, 9 Apr 2021 11:00:22 +0000 (UTC) Subject: Re: [PATCH 1/2] mm/vmscan: add sync_shrinkers function To: =?UTF-8?Q?Christian_K=c3=b6nig?= , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210409071725.1532-1-christian.koenig@amd.com> From: Vlastimil Babka Message-ID: <462c2a51-4aa8-47ba-1c67-171ca651b016@suse.cz> Date: Fri, 9 Apr 2021 13:00:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210409071725.1532-1-christian.koenig@amd.com> Content-Language: en-US X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: akpm@linux-foundation.org, ray.huang@amd.com Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" T24gNC85LzIxIDk6MTcgQU0sIENocmlzdGlhbiBLw7ZuaWcgd3JvdGU6Cj4gVG8gYmUgYWJsZSB0 byBzd2l0Y2ggdG8gYSBzcGlubG9jayBhbmQgcmVkdWNlIGxvY2sgY29udGVudGlvbiBpbiB0aGUg VFRNCj4gc2hyaW5rZXIgd2UgZG9uJ3Qgd2FudCB0byBob2xkIGEgbXV0ZXggd2hpbGUgdW5tYXBw aW5nIGFuZCBmcmVlaW5nIHBhZ2VzCj4gZnJvbSB0aGUgcG9vbC4KCkRvZXMgdXNpbmcgc3Bpbmxv Y2sgaW5zdGVhZCBvZiBtdXRleCByZWFsbHkgcmVkdWNlIGxvY2sgY29udGVudGlvbj8KCj4gQnV0 IHRoZW4gd2Ugc29tZWhvdyBuZWVkIHRvIHByZXZlbnQgYSByYWNlIGJldHdlZW4gKGZvciBleGFt cGxlKSB0aGUgc2hyaW5rZXIKPiB0cnlpbmcgdG8gZnJlZSBwYWdlcyBhbmQgaG90cGx1ZyB0cnlp bmcgdG8gcmVtb3ZlIHRoZSBkZXZpY2Ugd2hpY2ggdGhvc2UgcGFnZXMKPiBiZWxvbmcgdG8uCj4g Cj4gVGFraW5nIGFuZCByZWxlYXNpbmcgdGhlIHNocmlua2VyIHNlbWFwaG9yZSBvbiB0aGUgd3Jp dGUgc2lkZSBhZnRlcgo+IHVubWFwcGluZyBhbmQgZnJlZWluZyBhbGwgcGFnZXMgc2hvdWxkIG1h a2Ugc3VyZSB0aGF0IG5vIHNocmlua2VyIGlzIHJ1bm5pbmcgaW4KPiBwYXJhbGVsbCBhbnkgbW9y ZS4KClNvIHlvdSBleHBsYWluIHRoaXMgaW4gdGhpcyBjb21taXQgbG9nIGZvciBhZGRpbmcgdGhl IGZ1bmN0aW9uLCBidXQgdGhlbiB0aGUKbmV4dCBwYXRjaCBqdXN0IGFkZHMgYSBzeW5jX3Nocmlu a2VycygpIGNhbGwgd2l0aG91dCBhbnkgY29tbWVudC4gSSB3b3VsZCBleHBlY3QKdGhlcmUgYSBj b21tZW50IGV4cGxhaW5pbmcgd2h5IGl0J3MgZG9uZSB0aGVyZSAtIHdoYXQgaXQgcHJvdGVjdHMg YWdhaW5zdCwgYXMKaXQncyBub3QgYW4gb2J2aW91cyBwYXR0ZXJuIElNSE8uCgo+IFNpZ25lZC1v ZmYtYnk6IENocmlzdGlhbiBLw7ZuaWcgPGNocmlzdGlhbi5rb2VuaWdAYW1kLmNvbT4KPiAtLS0K PiAgaW5jbHVkZS9saW51eC9zaHJpbmtlci5oIHwgIDEgKwo+ICBtbS92bXNjYW4uYyAgICAgICAg ICAgICAgfCAxMCArKysrKysrKysrCj4gIDIgZmlsZXMgY2hhbmdlZCwgMTEgaW5zZXJ0aW9ucygr KQo+IAo+IGRpZmYgLS1naXQgYS9pbmNsdWRlL2xpbnV4L3Nocmlua2VyLmggYi9pbmNsdWRlL2xp bnV4L3Nocmlua2VyLmgKPiBpbmRleCAwZjgwMTIzNjUwZTIuLjZiNzVkYzM3MmZjZSAxMDA2NDQK PiAtLS0gYS9pbmNsdWRlL2xpbnV4L3Nocmlua2VyLmgKPiArKysgYi9pbmNsdWRlL2xpbnV4L3No cmlua2VyLmgKPiBAQCAtOTIsNCArOTIsNSBAQCBleHRlcm4gdm9pZCByZWdpc3Rlcl9zaHJpbmtl cl9wcmVwYXJlZChzdHJ1Y3Qgc2hyaW5rZXIgKnNocmlua2VyKTsKPiAgZXh0ZXJuIGludCByZWdp c3Rlcl9zaHJpbmtlcihzdHJ1Y3Qgc2hyaW5rZXIgKnNocmlua2VyKTsKPiAgZXh0ZXJuIHZvaWQg dW5yZWdpc3Rlcl9zaHJpbmtlcihzdHJ1Y3Qgc2hyaW5rZXIgKnNocmlua2VyKTsKPiAgZXh0ZXJu IHZvaWQgZnJlZV9wcmVhbGxvY2VkX3Nocmlua2VyKHN0cnVjdCBzaHJpbmtlciAqc2hyaW5rZXIp Owo+ICtleHRlcm4gdm9pZCBzeW5jX3Nocmlua2Vycyh2b2lkKTsKPiAgI2VuZGlmCj4gZGlmZiAt LWdpdCBhL21tL3Ztc2Nhbi5jIGIvbW0vdm1zY2FuLmMKPiBpbmRleCA1NjJlODdjYmQ3YTEuLjQ2 Y2Q5YzIxNWQ3MyAxMDA2NDQKPiAtLS0gYS9tbS92bXNjYW4uYwo+ICsrKyBiL21tL3Ztc2Nhbi5j Cj4gQEAgLTQwOCw2ICs0MDgsMTYgQEAgdm9pZCB1bnJlZ2lzdGVyX3Nocmlua2VyKHN0cnVjdCBz aHJpbmtlciAqc2hyaW5rZXIpCj4gIH0KPiAgRVhQT1JUX1NZTUJPTCh1bnJlZ2lzdGVyX3Nocmlu a2VyKTsKPiAgCj4gKy8qKgo+ICsgKiBzeW5jX3Nocmlua2VyIC0gV2FpdCBmb3IgYWxsIHJ1bm5p bmcgc2hyaW5rZXJzIHRvIGNvbXBsZXRlLgo+ICsgKi8KPiArdm9pZCBzeW5jX3Nocmlua2Vycyh2 b2lkKQo+ICt7Cj4gKwlkb3duX3dyaXRlKCZzaHJpbmtlcl9yd3NlbSk7Cj4gKwl1cF93cml0ZSgm c2hyaW5rZXJfcndzZW0pOwo+ICt9Cj4gK0VYUE9SVF9TWU1CT0woc3luY19zaHJpbmtlcnMpOwo+ ICsKPiAgI2RlZmluZSBTSFJJTktfQkFUQ0ggMTI4Cj4gIAo+ICBzdGF0aWMgdW5zaWduZWQgbG9u ZyBkb19zaHJpbmtfc2xhYihzdHJ1Y3Qgc2hyaW5rX2NvbnRyb2wgKnNocmlua2N0bCwKPiAKCl9f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCmRyaS1kZXZlbCBt YWlsaW5nIGxpc3QKZHJpLWRldmVsQGxpc3RzLmZyZWVkZXNrdG9wLm9yZwpodHRwczovL2xpc3Rz LmZyZWVkZXNrdG9wLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2RyaS1kZXZlbAo=