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Tue, 04 Jun 2024 05:03:49 -0700 (PDT) MIME-Version: 1.0 References: <20240601025536.25682-1-rgbi3307@naver.com> <57xfda6fbz6m4sig4kdyi5jinibcqycobwrpaih45cykfqyr5a@fstc2xjyw2x5> In-Reply-To: <57xfda6fbz6m4sig4kdyi5jinibcqycobwrpaih45cykfqyr5a@fstc2xjyw2x5> From: JaeJoon Jung Date: Tue, 4 Jun 2024 21:03:36 +0900 Message-ID: Subject: Re: [PATCH] maple_tree: add mas_node_count() before going to slow_path in mas_wr_modify() To: "Liam R. Howlett" , JaeJoon Jung , maple-tree@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 060541C002B X-Stat-Signature: k689n7w4na4yamcbxg13sctwwz7asu5c X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1717502630-342013 X-HE-Meta: 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 zmxshkYX KulnCYNGlglX5efrEdr521uQ1aJWwjFoWSvfxY9SoHzpimBXOZKO7Ozg272Yy7UF4t0Q0yyKA2nD7a8t2PTl2BQSbtwUWfsi5adRBlSUmy4bTVYgz+25tU2D3YZTOL3GI4Ffxbeou+T5zro/uTdU8K+K+sHJPkMw8KA9vCVPfPckVemaEDaouYWobgnXPrhu41LZNQe1li/q8hyJt1J+vrb/XQeOOXdkBAiY5Li1bvbkxo0oOPT5+m5GamFNz3CEoUvNo5S9lrt0Ku+bBCOx9YO8Jfu2fVdtPiJiHWcWjCyc1WYmYfHLDQtLYPM2lsQXn47CSSdIjc/sj+a099jTHuVwMdm5ZTg2zYraaHaLhEEFzPxtS8rq0bWYZ7LhX/Y7BxCr7DxgGPtIJ8JugGKYzrODAfEdpE2Z5do6ys1BPfUwUdsgDVpo9K/mfPbeMQOHOIE71 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000782, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello, Liam. As you pointed out, I did enough testing in the userspace and in previous versions of the kernel, but I was surprised that a syntax error occurred in making newest patch because of my careless mistake. I will be careful not to make this mistake again. And I am going to study the low memory situation in kernel space in more detail. Thank you very much for your detailed answer and explanation. Best regards, JaeJoon Jung On Mon, 3 Jun 2024 at 21:29, Liam R. Howlett wrote: > > * JaeJoon Jung [240602 05:06]: > > Hello, Liam. > > Thank you very much for the detailed answer and explanation. > > > > I tested this patch in userspace. > > In user space, this phenomenon always occurs when kmem_cache_alloc() > > is executed to allocate a new node. > > This is expected in the userspace test program. We test the error path > most frequently, with only a bypass for those who wish to test an > initial success - such as preallocations. I was concerned about the > testing since your first patch had a syntax error with a correction > quickly after. It is good news that you were able to find and use the > maple tree testing framework, though. > > > I will try to test it in more detail in kernel space. > > If you test in kernel space, you will have to hit a low memory scenario > to see a difference. stress-ng would probably help. > > > I will also refer to the notes from the email list you shared > > and send results once a more clear analysis has been made. > > I don't think you need to continue with this work as you will find that > the low memory situation is going to be rare and in a very slow path > already. > > Thanks, > Liam