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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 925481C0011 X-Stat-Signature: ma7nsibp1xpc3gzucdsc4d7zxd77cre4 X-Rspam-User: X-HE-Tag: 1706590348-93710 X-HE-Meta: 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 efQK5nTq 2jzj9YD4BE9g9ZlPANgAFs39AQXx35JdEBSIaM6JXmGtztizLbQ+T3CVMG56MtSfN+xo9D2RJ09YeSVU2CNJD9RHjtr2jnVsxENNH4kY5hT0eMkHJPepzJrqQ2CjIT73Yrrr7Gh5eMIyPZoqyhIRQur0mtmvFqOV+CDs1tDHyfeEaUC2WEud4HPQRDh0KFGMwG/sHdmWKnuCL06y6qa9kJpziK76mKtruqLJnEEDRmwJhN192GbIwGQv9D4T70xwy6KhG 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 1/29/24 17:21, Alexandru Elisei wrote: > Hi, > > On Mon, Jan 29, 2024 at 02:54:20PM +0530, Anshuman Khandual wrote: >> >> >> On 1/25/24 22:12, Alexandru Elisei wrote: >>> The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one >>> after each cma_alloc() function call. This is done even though cma_alloc() >>> can allocate an arbitrary number of CMA pages. When looking at >>> /proc/vmstat, the number of successful (or failed) cma_alloc() calls >>> doesn't tell much with regards to how many CMA pages were allocated via >>> cma_alloc() versus via the page allocator (regular allocation request or >>> PCP lists refill). >>> >>> This can also be rather confusing to a user who isn't familiar with the >>> code, since the unit of measurement for nr_free_cma is the number of pages, >>> but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() >>> function calls. >>> >>> Let's make this consistent, and arguably more useful, by having >>> CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and >>> CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to >>> allocate. >>> >>> For users that wish to track the number of cma_alloc() calls, there are >>> tracepoints for that already implemented. >>> >>> Signed-off-by: Alexandru Elisei >>> --- >>> mm/cma.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/cma.c b/mm/cma.c >>> index f49c95f8ee37..dbf7fe8cb1bd 100644 >>> --- a/mm/cma.c >>> +++ b/mm/cma.c >>> @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, >>> pr_debug("%s(): returned %p\n", __func__, page); >>> out: >>> if (page) { >>> - count_vm_event(CMA_ALLOC_SUCCESS); >>> + count_vm_events(CMA_ALLOC_SUCCESS, count); >>> cma_sysfs_account_success_pages(cma, count); >>> } else { >>> - count_vm_event(CMA_ALLOC_FAIL); >>> + count_vm_events(CMA_ALLOC_FAIL, count); >>> if (cma) >>> cma_sysfs_account_fail_pages(cma, count); >>> } >> >> Without getting into the merits of this patch - which is actually trying to do >> semantics change to /proc/vmstat, wondering how is this even related to this >> particular series ? If required this could be debated on it's on separately. > > Having the number of CMA pages allocated and the number of CMA pages freed > allows someone to infer how many tagged pages are in use at a given time: That should not be done in CMA which is a generic multi purpose allocator. > (allocated CMA pages - CMA pages allocated by drivers* - CMA pages > released) * 32. That is valuable information for software and hardware > designers. > > Besides that, for every iteration of the series, this has proven invaluable > for discovering bugs with freeing and/or reserving tag storage pages. I am afraid that might not be enough justification for getting something merged mainline. > > *that would require userspace reading cma_alloc_success and > cma_release_success before any tagged allocations are performed. While assuming that no other non-memory-tagged CMA based allocation amd free call happens in the meantime ? That would be on real thin ice. I suppose arm64 tagged memory specific allocation or free related counters need to be created on the caller side, including arch_free_pages_prepare().