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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 68A11C07D59 for ; Sat, 25 Nov 2023 17:38:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231808AbjKYRiA (ORCPT ); Sat, 25 Nov 2023 12:38:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229782AbjKYRh6 (ORCPT ); Sat, 25 Nov 2023 12:37:58 -0500 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A696127 for ; Sat, 25 Nov 2023 09:38:05 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-da3dd6a72a7so3501886276.0 for ; Sat, 25 Nov 2023 09:38:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1700933884; x=1701538684; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=/OjN2yjM4lGF+xoZzPeOmLggYv6X6PaCmv884vExzhQ=; b=Sb4za/p9PvTD0oIEk6DlS068u8izzt+Sbq6UOPQjqx4DXCVv3RzHfPPtGJvLBf9rEY gx3iWBUNixvRIlAXWhsJqAEWH/lDvJto9kE+a6x9TJTskmY5EDfzR2IFfD3egqbZ8WWY 9vZKRKCQWjUxR2eOC4eKFtWqyYFL6QcpZwKE8lVHFIuhFyboHHyGXplhidwIClLPfVqB DVNX4I/6qtjEZsFqaCERd12IM72HcJxqdb05CIp1TkG5vxAGsXeQT/XWRRrKRAWBpddK hXY29g905eyC4DjR98qVwDL/n+f4BRWMcS840qldcg6y0MGMW2ZlBTuRJLUf/X6SIiwT Gbmg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1700933884; x=1701538684; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=/OjN2yjM4lGF+xoZzPeOmLggYv6X6PaCmv884vExzhQ=; b=F0vwmysKlQ2Y/Xc7uHS0ddpLamcnx9RLkX8CoIy+W4vR/quUzRN9HefVUKFBiN7J5s vPPhB2Ljr9ebu2h14HiKCS2gTQQtTMUu4A7MgPg2OJF0ZMmpcoghSHMqazVjKImEosDL v+jnb+KZmHagrdqav84QbqZXKauWQmls/v9dUax8pxyrgxrro1J6mjqkV5sSG1jXvJGO DC6bOf70sr2ISQHVDQ8izzoAg8m/zt4dtQjfyNoPZvExUYSrxetx29iaCX7D+rl2fSOl i21vLpXoj1jy8itDIMayUI/ss2XM5H+tsxhSPbbr02e88fOsJlPY7jAb+8nJyOngvKn0 /Lhw== X-Gm-Message-State: AOJu0Yw/yOPEjCEm+KJNmRzM2xU8Pxlr4A2/zE4pD+7A1ozvu5dzn6zh VjtU+MYEBXrbn+Hp/Gd7KO+omXfEttnMSg== X-Google-Smtp-Source: AGHT+IHnGysxB/944b9w0n+byMEk08BlMdz921PvjzprbIkgHG0uwA4pdEh20uVwBEuI1Q+ppKReG75nHOmEVQ== X-Received: from shakeelb.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:262e]) (user=shakeelb job=sendgmr) by 2002:a25:3d44:0:b0:da0:567d:f819 with SMTP id k65-20020a253d44000000b00da0567df819mr220022yba.10.1700933884073; Sat, 25 Nov 2023 09:38:04 -0800 (PST) Date: Sat, 25 Nov 2023 17:38:02 +0000 In-Reply-To: <20231125080137.2fhmi4374yxqjyix@CAB-WSD-L081021> Mime-Version: 1.0 References: <20231123193937.11628-1-ddrokosov@salutedevices.com> <20231123193937.11628-3-ddrokosov@salutedevices.com> <20231125063616.dex3kh3ea43ceyu3@google.com> <20231125080137.2fhmi4374yxqjyix@CAB-WSD-L081021> Message-ID: <20231125173802.pfhalf27kxk3wavy@google.com> Subject: Re: [PATCH v3 2/2] mm: memcg: introduce new event to trace shrink_memcg From: Shakeel Butt To: Dmitry Rokosov Cc: rostedt@goodmis.org, mhiramat@kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, muchun.song@linux.dev, mhocko@suse.com, akpm@linux-foundation.org, kernel@sberdevices.ru, rockosov@gmail.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Nov 25, 2023 at 11:01:37AM +0300, Dmitry Rokosov wrote: [...] > > > + trace_mm_vmscan_memcg_shrink_begin(sc->order, > > > + sc->gfp_mask, > > > + memcg); > > > + > > > > If you place the start of the trace here, you may have only the begin > > trace for memcgs whose usage are below their min or low limits. Is that > > fine? Otherwise you can put it just before shrink_lruvec() call. > > > > From my point of view, it's fine. For situations like the one you > described, when we only see the begin() tracepoint raised without the > end(), we understand that reclaim requests are being made but cannot be > satisfied due to certain conditions within memcg (such as limits). > > There may be some spam tracepoints in the trace pipe, which is a disadvantage > of this approach. > > How important do you think it is to understand such situations? Or do > you suggest moving the begin() tracepoint after the memcg limits checks > and don't care about it? > I was mainly wondering if that is intentional. It seems like you as first user of this trace has a need to know that a reclaim for a given memcg was triggered but due to min/low limits no reclaim was done. This is a totally reasonable use-case.