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Tue, 30 Jun 2020 13:46:09 -0700 (PDT) Received: from xz-x1.redhat.com ([2607:9880:19c0:32::2]) by smtp.gmail.com with ESMTPSA id d13sm3830829qkj.27.2020.06.30.13.46.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2020 13:46:08 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , peterx@redhat.com, John Hubbard , Michael Ellerman , Gerald Schaefer , Andrea Arcangeli , Linus Torvalds , Will Deacon Subject: [PATCH v4 25/26] mm: Clean up the last pieces of page fault accountings Date: Tue, 30 Jun 2020 16:46:07 -0400 Message-Id: <20200630204607.39688-1-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 86CDD8003436 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 Content-Transfer-Encoding: quoted-printable 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: Here're the last pieces of page fault accounting that were still done out= side handle_mm_fault() where we still have regs=3D=3DNULL when calling handle_= mm_fault(): arch/powerpc/mm/copro_fault.c: copro_handle_mm_fault arch/sparc/mm/fault_32.c: force_user_fault arch/um/kernel/trap.c: handle_page_fault mm/gup.c: faultin_page fixup_user_fault mm/hmm.c: hmm_vma_fault mm/ksm.c: break_ksm Some of them has the issue of duplicated accounting for page fault retrie= s. Some of them didn't do the accounting at all. This patch cleans all these up by letting handle_mm_fault() to do per-tas= k page fault accounting even if regs=3D=3DNULL (though we'll still skip the perf= event accountings). With that, we can safely remove all the outliers now. There's another functional change in that now we account the page faults = to the caller of gup, rather than the task_struct that passed into the gup code.= More information of this can be found at [1]. After this patch, below things should never be touched again outside handle_mm_fault(): - task_struct.[maj|min]_flt - PERF_COUNT_SW_PAGE_FAULTS_[MAJ|MIN] [1] https://lore.kernel.org/lkml/CAHk-=3Dwj_V2Tps2QrMn20_W0OJF9xqNh52XSGA= 42s-ZJ8Y+GyKw@mail.gmail.com/ Signed-off-by: Peter Xu --- arch/powerpc/mm/copro_fault.c | 5 ----- arch/um/kernel/trap.c | 4 ---- mm/gup.c | 13 ------------- mm/memory.c | 19 ++++++++++++------- 4 files changed, 12 insertions(+), 29 deletions(-) diff --git a/arch/powerpc/mm/copro_fault.c b/arch/powerpc/mm/copro_fault.= c index 2d0276abe0a6..8acd00178956 100644 --- a/arch/powerpc/mm/copro_fault.c +++ b/arch/powerpc/mm/copro_fault.c @@ -76,11 +76,6 @@ int copro_handle_mm_fault(struct mm_struct *mm, unsign= ed long ea, BUG(); } =20 - if (*flt & VM_FAULT_MAJOR) - current->maj_flt++; - else - current->min_flt++; - out_unlock: mmap_read_unlock(mm); return ret; diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c index 8d9870d76da1..ad12f78bda7e 100644 --- a/arch/um/kernel/trap.c +++ b/arch/um/kernel/trap.c @@ -88,10 +88,6 @@ int handle_page_fault(unsigned long address, unsigned = long ip, BUG(); } if (flags & FAULT_FLAG_ALLOW_RETRY) { - if (fault & VM_FAULT_MAJOR) - current->maj_flt++; - else - current->min_flt++; if (fault & VM_FAULT_RETRY) { flags |=3D FAULT_FLAG_TRIED; =20 diff --git a/mm/gup.c b/mm/gup.c index 53ad15629014..89b18c407ad2 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -893,13 +893,6 @@ static int faultin_page(struct task_struct *tsk, str= uct vm_area_struct *vma, BUG(); } =20 - if (tsk) { - if (ret & VM_FAULT_MAJOR) - tsk->maj_flt++; - else - tsk->min_flt++; - } - if (ret & VM_FAULT_RETRY) { if (locked && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) *locked =3D 0; @@ -1255,12 +1248,6 @@ int fixup_user_fault(struct task_struct *tsk, stru= ct mm_struct *mm, goto retry; } =20 - if (tsk) { - if (major) - tsk->maj_flt++; - else - tsk->min_flt++; - } return 0; } EXPORT_SYMBOL_GPL(fixup_user_fault); diff --git a/mm/memory.c b/mm/memory.c index e594d5cdcaa0..00d96ae9464c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4365,6 +4365,8 @@ static vm_fault_t __handle_mm_fault(struct vm_area_= struct *vma, /** * mm_account_fault - Do page fault accountings * @regs: the pt_regs struct pointer. When set to NULL, will skip accou= nting + * of perf event counters, but we'll still do the per-task accoun= ting to + * the task who triggered this page fault. * @address: faulted address. * @major: whether this is a major fault. * @@ -4380,16 +4382,18 @@ static vm_fault_t __handle_mm_fault(struct vm_are= a_struct *vma, static inline void mm_account_fault(struct pt_regs *regs, unsigned long address, bool major) { + if (major) + current->maj_flt++; + else + current->min_flt++; + if (!regs) return; =20 - if (major) { - current->maj_flt++; + if (major) perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); - } else { - current->min_flt++; + else perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); - } } =20 /* @@ -4462,8 +4466,9 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *v= ma, unsigned long address, * fault is VM_FAULT_MAJOR, or if it was a retry (which implies that * we couldn't handle it immediately previously). * - * - If the fault is done for GUP, regs will be NULL and no accounting - * will be done. + * - If the fault is done for GUP, regs will be NULL and we only do + * the accounting for the per thread fault counters who triggered + * the fault, and we skip the perf event updates. */ mm_account_fault(regs, address, (ret & VM_FAULT_MAJOR) || (flags & FAULT_FLAG_TRIED)); --=20 2.26.2