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AJvYcCVSMxQvX8nLt02sgjCvCSwYUK8XFgqzgIksScgUFyfCgOw/alGKrp+IPwdPYi9pfidBV3RXleSc3kU5y/uxPRw64Lo= X-Gm-Message-State: AOJu0YykVCcO3jW0lfyHocCn5OUL3fYRf7T5wgQg438i4eATpuQdy95/ Iw9s68qV1WD4nICgmUPksUcSiEU2DwWxctFbc2dXqe4ebHYYYnG28uSZcmzKDiHqYTzsTaAEI+8 P3y1z6wSiDfLt+BU3KqdasgSi8K0= X-Google-Smtp-Source: AGHT+IGmzyvg9bIXR+IslMkKfBb2Iawh5jF++69PND/traAmW5TAvvfqtm3V/SUjuRS/55t07q0rI88UIZL6F2hPbO8= X-Received: by 2002:a0c:df8a:0:b0:690:690:ce84 with SMTP id w10-20020a0cdf8a000000b006900690ce84mr2071842qvl.6.1709042639584; Tue, 27 Feb 2024 06:03:59 -0800 (PST) MIME-Version: 1.0 References: <20240225114204.50459-1-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Tue, 27 Feb 2024 22:03:22 +0800 Message-ID: Subject: Re: [RFC PATCH] mm: Add reclaim type to memory.reclaim To: Michal Hocko Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, roman.gushchin@linux.dev, shakeelb@google.com, muchun.song@linux.dev, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 8EE044004B X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: y3771ktpnd1z13jxu649ttu49bgtu6p9 X-HE-Tag: 1709042640-70652 X-HE-Meta: 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 XSGzFKmf +4nhqXvdDvU/p2O52j94952xv7DFRTntg6xy850oevDY6DRIyHINu28/IPAZVWFX41bWGFrUXdK9XsZEBiFCNGT/WW4qSPOEIPh+9zsW0LkMqGOG0xkRmV4qqlUxYA017Ds2iWeRf94iiESTF+havIUwVlMh8ZHSnhvOdtaqN057PFMksy5tElXtLMkf+9Q4I3Dfc2BRjQVl2gcjXGMpGZ0t39XLg1iLP5GsEPGgfdmoLQLS7n5sfmqsWNbabcqtfPmWEOWA8nzqfHRwmkGtXQP3D8uiH4UD9TNNWr6oTqbEMpnss/k/6PIkCQqlJV5iDgwauZnYhKXc++Rmgthmwrj0OmpgmOmYevalnYxMDj7baWtKuap4eqN/R+xYxwIP/t2WQ2IqWAz6wHsQbUm/t4bxu5R8xoa6zTkE11QZAHVp36+5NMSdVBX7wk4THAoyA7kl4 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000150, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Feb 27, 2024 at 9:20=E2=80=AFPM Michal Hocko wrot= e: > > On Tue 27-02-24 18:06:05, Yafang Shao wrote: > > On Tue, Feb 27, 2024 at 5:45=E2=80=AFPM Michal Hocko = wrote: > [...] > > > > Reclaiming numerous dentries through force_empty can also lead to > > > > potential issues, which is why we attempt to shrink the slab gradua= lly > > > > to mitigate them. However, it's important to note that the underlyi= ng > > > > causes of the issues in force_empty and rmdir are not identical, as > > > > they involve different locks. > > > > > > Please be more specific about those issues. > > > > Both of these issues stem from lock contention: > > > > - rmdir > > When executing rmdir, the lock of the inode of the empty directory is > > held. If this directory contains numerous negative dentries, this lock > > is held for an extended duration. Consequently, if other processes > > attempt to acquire this lock, they are blocked. > > A simple reproducer involves: > > > > 1. Generating numerous negative dentries in an empty directory. > > 2. Running `rmdir ~/test` and `ls ~/` concurrently. > > I fail to see how is this relevant to memcg reclaim It appears there might still be some misunderstanding regarding the issue at hand. The numerous negative dentries are generated within a memcg. I simplified the explanation by omitting the memcg context. > > > This setup demonstrates that ls takes a significant amount of time to > > complete due to lock contention. > > > > - force_empty > > Force_empty holds the lock of super_block->dentry_list. However, I > > haven't yet had the opportunity to produce a specific example to > > illustrate this issue. > > OK, get back to us once you can identify an actual problem. We might be Pls. take a look at the force_empty->prune_dcache_sb->shrink_dentry_list. > talking about different things here though. My question is directed at > existing memcg interfaces to reclaim the memory. That would be legacy > (and effectively deprecated) force_empty and memory.reclaim that we > have. --=20 Regards Yafang