From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZXULRDIp" Received: from mail-oi1-x234.google.com (mail-oi1-x234.google.com [IPv6:2607:f8b0:4864:20::234]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2CA94D3; Wed, 6 Dec 2023 08:52:44 -0800 (PST) Received: by mail-oi1-x234.google.com with SMTP id 5614622812f47-3b845ba9ba9so10155b6e.3; Wed, 06 Dec 2023 08:52:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1701881563; x=1702486363; darn=vger.kernel.org; h=cc:to:subject:message-id:date:from:references:in-reply-to :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=i1au5lbtdhuYhTzxu7K3e1mZkKqka6jLLtZkjNaoKMc=; b=ZXULRDIpSZOkiumlJHfa69UVuyRP0DruUZNJpc+Hh4BvfpWz1YPdOgpqiR4TV1picY uGRQqisr0a5fDaf8OG639RBlSoJ0uRYDYav0OW3V6x8VU1fMO4TJSHqcNSD42LKoFyCt O6flSvpCm1gdyzuzPieDpSkJn0h3tGOjmSUdTPzzBlpwEn//ssCoRZhIl9hiqqPHuJGi SzDNC+kqCEDTqzT/MAcEepey/BkWw96a/YsEnRU7tyNLEwRvUY+9FtGiN6MBEEbWz2J5 bM9fJSu9e6LWlwF6m/kYiiffUk311orf2vh9BltaMjEYFI8x5103tY/vBmSFrwNQHeRA phLg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1701881563; x=1702486363; h=cc:to:subject:message-id:date:from:references:in-reply-to :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=i1au5lbtdhuYhTzxu7K3e1mZkKqka6jLLtZkjNaoKMc=; b=FHUvE5bqPa2tTAndkmlIcWfyxN5r6mNjHKMfL8hNaaN59ftjA50M9QQx1G4oSSEhj9 TiLh27S4ON0dMBS9uwqOSSErTQ2hO2mf2DQoupRzZTNGuNzbb2muQQdDpcaiIOUB9J/R wmU6jNHDNPSW5r8oWovcBsiMBHSLvsjGbN3Y48QhDfFY9DuGzcjIE/3WdZA8hc/KnyfW 4UGSJP3pIX9yCmm1vHmdpnhoRRsubMpvrV7ic92UH5UC4RGZCYXwentVFlGXcE63NgLq sXWclAjWJ5SeinWkVCcOAv6ab/UWMhEOwEZg1ktqUsj8YjZMxIDKU87PvNcR64WwBbXR wnMg== X-Gm-Message-State: AOJu0YwL0PeL63ja9Fex5aIaSlm7xPutT0LYb8k1InQqYAsIL31ozXW5 GZYTLBUQfSD9EKoyvayKhi2dDI/Hmr+s/Hj8Wmo= X-Google-Smtp-Source: AGHT+IGZ/Yr5F7fr0x3yUHZ3H8FzlhrdgaoQi9g9SY9SBjIS2V506x0YzxsM95+SBtT/PUWyn/Ecfay+HG2v633hkYE= X-Received: by 2002:a05:6870:1711:b0:1fb:75c:3feb with SMTP id h17-20020a056870171100b001fb075c3febmr1324530oae.75.1701881563431; Wed, 06 Dec 2023 08:52:43 -0800 (PST) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Received: by 2002:a05:6802:30f:b0:50c:13ee:b03d with HTTP; Wed, 6 Dec 2023 08:52:43 -0800 (PST) In-Reply-To: <20231206164513.GO1674809@ZenIV> References: <20231201040951.GO38156@ZenIV> <20231201065602.GP38156@ZenIV> <20231201200446.GA1431056@ZenIV> <20231204195321.GA1674809@ZenIV> <20231206054946.GM1674809@ZenIV> <20231206161509.GN1674809@ZenIV> <20231206163010.445vjwmfwwvv65su@f> <20231206164513.GO1674809@ZenIV> From: Mateusz Guzik Date: Wed, 6 Dec 2023 17:52:43 +0100 Message-ID: Subject: Re: [viro-vfs:work.dcache2] [__dentry_kill()] 1b738f196e: stress-ng.sysinfo.ops_per_sec -27.2% regression To: Al Viro Cc: Oliver Sang , oe-lkp@lists.linux.dev, lkp@intel.com, linux-fsdevel@vger.kernel.org, Christian Brauner , linux-doc@vger.kernel.org, ying.huang@intel.com, feng.tang@intel.com, fengwei.yin@intel.com, Linus Torvalds Content-Type: text/plain; charset="UTF-8" On 12/6/23, Al Viro wrote: > On Wed, Dec 06, 2023 at 05:30:10PM +0100, Mateusz Guzik wrote: > >> > What the hell is going on? Was ->d_lock on parent serving as a throttle >> > and reducing >> > the access rate to something badly contended down the road? I don't see >> > anything >> > of that sort in the profile changes, though... > >> Not an outlandish claim would be that after you stopped taking one of >> them, spinning went down and more traffic was put on locks which *can* >> put their consumers off cpu (and which *do* do it in this test). > > That's about the only guess I've got (see above), but if that's the case, > which lock would > that be? > >> All that said I think it would help if these reports started including >> off cpu time (along with bt) at least for spawned threads. > Given backtracs I posted it's at least root->kernfs_iattr_rwsem (see kernfs_iop_permission), but there may be more. Ultimately I expect would be easy to answer if one was to rebuild with lockstat. I may end up doing it tomorrow if there is a problem testing this on your end. -- Mateusz Guzik