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Tue, 25 Jun 2024 10:36:53 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id RvegOcWdemYsXwAAD6G6ig (envelope-from ); Tue, 25 Jun 2024 10:36:53 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 90444A090B; Tue, 25 Jun 2024 12:36:53 +0200 (CEST) Date: Tue, 25 Jun 2024 12:36:53 +0200 From: Jan Kara To: zippermonkey Cc: zhangpengpeng0808@gmail.com, akpm@linux-foundation.org, bruzzhang@tencent.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, vernhao@tencent.com, willy@infradead.org, zigiwang@tencent.com, jack@suse.cz Subject: Re: [PATCH RFC] mm/readahead: Fix repeat initial_readahead Message-ID: <20240625103653.uzabtus3yq2lo3o6@quack3> References: <20240618114941.5935-1-zhangpengpeng0808@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Action: no action X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BE69840014 X-Stat-Signature: 8ycedeosmapftga99hpcacbnjm8fihzd X-Rspam-User: X-HE-Tag: 1719311815-352809 X-HE-Meta: U2FsdGVkX1/a1DYzu2ynNRody+v+oq9ydzruTul4VBWDV/s4OWiF0DrM8v29mBtiy9sTdcLmDfH2DlYulO3LAHBfJU0bFRVEb3O7qOIAuC+XvUVkT2ZbJ3PsbG7nc2MBE9fuuYaRDmVod31Sf5dgdq9GAYqdNY0JYKaws5TstrQMUpcwsDKYrTRPsPP+5YkIUDla26r4t6j66dlxgztLY+N0yrj1HTySSPX45wDgbamOMrRYgWxFBdfcwdHpnrIBqr+4KV+IQwnPdS5V/JLeCYt8HdNpsuZs2SjfIJqib5TqNIbL76fV8YIKBsfrXpXtjB8XuwriZSOirF+csEkA1JITiPIYOn++KcA1AOJLeuF2E/JB1alqDU0iz6SNw71DXj4o7cA1a4St1qW1veZk2KqPRuAjH9LqqBz+p7GebwO9/AG3eeErTOmwDE0VmnBZ3nOYolXaL/DMBIR1ug8+x7TBiysFV8gsKX+Xw0i9AY0iUx6pfMJmJLSHtpG54FKjKRoipGUoln9aps8SasDGxoLnIE4uycN7WWoIyDCgTI+r/1z3rHtsVYy3Mww67PVbKD/OulHyJ/4D8IeycyCxXOAIZR4SZbZmXQWglv2H230LnA8ai4RMHCpHq3sJBxe0SJzwlJrtDXw+5gq8sYBK2CrR+oDaoNtk65fcgEGxVjNLT9aglyQLx3Nd7ZnbWz+RqPBUBPxIKa7sJnY5oeeYsg2Gp8eUbVYY+Vztxw3xdndv0g9lTLfwYaSfSuDMvGaguTUyXhre+tU9gZhAz+8gjT3auy4PgEJBoA00APYYgyB9Z2gTo7mchwaiV3c7xrY+rL0amYpEIA//YBhM4QEANTe/Fi2/VLOPHg2eukPJZ/U5v4yyAqeUfnVL0/L4p+7+N0Ml384Vmp7mZnjiuaZBryiL+WWdpMr5Z1Ww8thKKMm9ot1izW3AfD9DEJzfEOSWfFYYu29H7q0YTu31shz K+4T5MA5 eJ5+axK0mLtNSXuchfMP821OuWvQwaoGkC/ebWt0l/4LExs5TL6+IdcQfLXOmloKR3MYXPEVS6Npcxme9mb36n2lbCPddTqVdffCOnP1CSnY46UpWjdAym1TV7IdyP0Cvw4retO+Wvmdw2xSOKIevD/yXxOvDf/71ttM0Fb0Xx/ZVbAOYdYkU33GD08mttmUH4f8STHzQXoNzrLhRbkUSOGPjFi869nk9qhWGQntICBcrxYxhgLndsT5m9c7jTDikSlTBHw/ryRZBouhXRqfBFq3s19J+w5tsgLNPHg6W+hKQNicS3EW5s4y/dpkln9BL7X3PePKWfJoqcyIzWVqnW8buALlEg0pDHWJBjZJUwjEQPB1kiYOuwDCwZxDpidZ7ZnYp842ajMPEEryjAYhG3Uj08qijiDyBc7FsntHA54kbS6E= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 25-06-24 14:28:34, zippermonkey wrote: > To illustrate this problem, I created the following example: > > Assuming that the process reads sequentially from the beginning of the file > and > calls the `page_cache_sync_readahead` function. In this sync readahead > function, > since the index is 0, it will proceed to `initial_readahead` and initialize > `ra_state`. It allocates a folio with an order of 2 and marks it as > PG_readahead. > Next, because` (folio_test_readahead(folio))` is true, the > page_cache_async_ra > function is called, which causes the `ra_state` to be initialized again. Good spotting guys! There are actually more problems in the readahead code. I have just pushed out a patch series [1] addressing several issues that should also address the problem you've found. Can you please test whether it provides a similar speedup as your fix (sorry, I forgot to CC you on the series)? Thanks! [1] https://lore.kernel.org/20240625100859.15507-1-jack@suse.cz Honza -- Jan Kara SUSE Labs, CR