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Mon, 10 Feb 2025 10:18:18 -0800 (PST) MIME-Version: 1.0 References: <20250206185109.1210657-1-fvdl@google.com> <20250206185109.1210657-2-fvdl@google.com> In-Reply-To: From: Frank van der Linden Date: Mon, 10 Feb 2025 10:18:07 -0800 X-Gm-Features: AWEUYZlxwABmR4cpB9nR60jmL250rbMazLScEgkq5SHVd2OrPlsMf17BTN_54p4 Message-ID: Subject: Re: [PATCH v3 01/28] mm/cma: export total and free number of pages for CMA areas To: Oscar Salvador Cc: akpm@linux-foundation.org, muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yuzhao@google.com, usamaarif642@gmail.com, joao.m.martins@oracle.com, roman.gushchin@linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: B51DE40004 X-Stat-Signature: yo5rop96w5yninhtnxooo3cdqppbfsr1 X-Rspamd-Server: rspam03 X-HE-Tag: 1739211499-369892 X-HE-Meta: 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 Q0ikD5n6 nX+/QCNDa/p75+Pxu5PSE3TagZdUAi6OMaZpFd2AqsMHQK4XW3Pj+sWZnZDapQ/ZpP+2WRggz48SacEPon5qLS8FgNqhxIJTC/GOldaREsM0W1OQMBiW+q5z5bsnOUNQy32HP9cKthGsYF0hct+0QiRTmKthUFDCExeFBTTFTTcYGhSPv5VJhXJSlxU42Bfeiqpy9P0509CcU8tY8FXoEjxz3RBor/lYaklwEpiLtOL20LPh+28E1uHx4ig== X-Bogosity: Ham, tests=bogofilter, spamicity=0.001547, 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 Mon, Feb 10, 2025 at 2:22=E2=80=AFAM Oscar Salvador = wrote: > > On Thu, Feb 06, 2025 at 06:50:41PM +0000, Frank van der Linden wrote: > > In addition to the number of allocations and releases, system > > management software may like to be aware of the size of CMA > > areas, and how many pages are available in it. This information > > is currently not available, so export it in total_page and > > available_pages, respectively. > > > > The name 'available_pages' was picked over 'free_pages' because > > 'free' implies that the pages are unused. But they might not > > be, they just haven't been used by cma_alloc > > > > The number of available pages is tracked regardless of > > CONFIG_CMA_SYSFS, allowing for a few minor shortcuts in > > the code, avoiding bitmap operations. > > > > Signed-off-by: Frank van der Linden > > LGTM, > > nit below > > Reviewed-by: Oscar Salvador Thanks for the review! > > > --- > ... > > @@ -444,6 +445,14 @@ static struct page *__cma_alloc(struct cma *cma, u= nsigned long count, > > > > for (;;) { > > spin_lock_irq(&cma->lock); > > + /* > > + * If the request is larger than the available number > > + * of pages, stop right away. > > + */ > > + if (count > cma->available_count) { > > + spin_unlock_irq(&cma->lock); > > + break; > > + } > > bitmap_no =3D bitmap_find_next_zero_area_off(cma->bitmap, > > bitmap_maxno, start, bitmap_count, mask, > > offset); > > @@ -452,6 +461,7 @@ static struct page *__cma_alloc(struct cma *cma, un= signed long count, > > break; > > } > > bitmap_set(cma->bitmap, bitmap_no, bitmap_count); > > + cma->available_count -=3D count; > > I wonder whether we should have a cma_bitmat_set, so available_count woul= d be > touched in there. Yeah, I initially thought so as well. Then I realized that for one of the later patches (early CMA reservations), I'd need to decouple the bitmap set and adjusting available_count again. For cma_reserve_early, you don't have a bitmap yet, but you can use available_count to see if you can get what you want. So, I decided to not combine the two. - Frank