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Peter Anvin" , linux-perf-users@vger.kernel.org Subject: Re: [PATCH RFC 02/14] perf/ring_buffer: stop using PG_private as AUX page high-order marker Date: Sat, 1 Aug 2026 07:32:26 -0700 Message-ID: <20260801143227.1267657-1-usama.arif@linux.dev> In-Reply-To: <20260731-remove-pg_private-v1-2-142c97ba3562@nvidia.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: C2C6F180003 X-Rspamd-Server: rspam01 X-Stat-Signature: t7hnq6zcz3wmduwhma9g6m1tcsgzji6f X-HE-Tag: 1785594760-943973 X-HE-Meta: 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 3pPank07 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 31 Jul 2026 22:13:25 -0400 Zi Yan wrote: > A high-order AUX page sets PG_private on its first page and stores the > order in first_page->private. Stop using PG_private and check > first_page->private for AUX page order only ring buffer and its users. > nit: only "in the" ring buffer? > It prepares for a future commit that remove PG_private. > > No functional change intended. > > Assisted-by: Claude:claude-opus-4-8 > Assisted-by: Codex:gpt-5 > Signed-off-by: Zi Yan > To: Peter Zijlstra > To: Ingo Molnar > To: Arnaldo Carvalho de Melo > To: Namhyung Kim > To: Thomas Gleixner > To: Borislav Petkov > To: Dave Hansen > To: x86@kernel.org > Cc: Mark Rutland > Cc: Alexander Shishkin > Cc: Jiri Olsa > Cc: Ian Rogers > Cc: Adrian Hunter > Cc: James Clark > Cc: "H. Peter Anvin" > Cc: linux-perf-users@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > --- > arch/x86/events/intel/bts.c | 3 --- > arch/x86/events/intel/pt.c | 6 ++---- > kernel/events/ring_buffer.c | 7 +++---- > 3 files changed, 5 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c > index cbac54cb3a9ec..5849392cf26d5 100644 > --- a/arch/x86/events/intel/bts.c > +++ b/arch/x86/events/intel/bts.c > @@ -66,9 +66,6 @@ static struct pmu bts_pmu; > > static int buf_nr_pages(struct page *page) > { > - if (!PagePrivate(page)) > - return 1; > - For order 0, 1 << 0 is 1, which is exactly what the !PagePrivate(page) so LGTM. The commit message probably needs more text but everything else looks good. Feel free to add Acked-by: Usama Arif > return 1 << page_private(page); > } > > diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c > index b5726b50e77db..29d8b4a3560cd 100644 > --- a/arch/x86/events/intel/pt.c > +++ b/arch/x86/events/intel/pt.c > @@ -774,8 +774,7 @@ static int topa_insert_pages(struct pt_buffer *buf, int cpu, gfp_t gfp) > struct page *p; > > p = virt_to_page(buf->data_pages[buf->nr_pages]); > - if (PagePrivate(p)) > - order = page_private(p); > + order = page_private(p); > > if (topa_table_full(topa)) { > topa = topa_alloc(cpu, gfp); > @@ -1289,8 +1288,7 @@ static int pt_buffer_try_single(struct pt_buffer *buf, int nr_pages) > if (!intel_pt_validate_hw_cap(PT_CAP_single_range_output)) > goto out; > > - if (PagePrivate(p)) > - order = page_private(p); > + order = page_private(p); > > if (1 << order != nr_pages) > goto out; > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c > index 9fe92161715e0..061b5cb222266 100644 > --- a/kernel/events/ring_buffer.c > +++ b/kernel/events/ring_buffer.c > @@ -630,11 +630,10 @@ static struct page *rb_alloc_aux_page(int node, int order) > /* > * Communicate the allocation size to the driver: > * if we managed to secure a high-order allocation, > - * set its first page's private to this order; > - * !PagePrivate(page) means it's just a normal page. > + * set its first page's private to this order, otherwise page's > + * private remains zero. > */ > split_page(page, order); > - SetPagePrivate(page); > set_page_private(page, order); > } > > @@ -645,7 +644,7 @@ static void rb_free_aux_page(struct perf_buffer *rb, int idx) > { > struct page *page = virt_to_page(rb->aux_pages[idx]); > > - ClearPagePrivate(page); > + set_page_private(page, 0); > __free_page(page); > } > > > -- > 2.53.0 > >