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d="scan'208";a="96581669" From: Andrew Cooper To: Xen-devel CC: Andrew Cooper , Jan Beulich , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Wei Liu , Stefano Stabellini , Julien Grall , Volodymyr Babchuk , Bertrand Marquis Subject: [PATCH RFC] xen: Annotate printk() as cold Date: Mon, 20 Feb 2023 13:13:25 +0000 Message-ID: <20230220131325.1524786-1-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @citrix.com) X-ZM-MESSAGEID: 1676898851823100001 There is no such thing as a fastpath with a printk() on it, making printk()= an excellent heuristic for slowpaths. Net delta is: add/remove: 595/2 grow/shrink: 56/762 up/down: 70879/-87331 (-16452) Total: Before=3D4085425, After=3D4068973, chg -0.40% because cold functions are optimised differently. For example, one function with a particularly large swing is: vmcs_dump_vcpu.cold - 2172 +2172 vmcs_dump_vcpu 7030 408 -6622 with a net delta of 7030 down to 4450. Signed-off-by: Andrew Cooper Acked-by: Jan Beulich --- CC: Jan Beulich CC: Roger Pau Monn=C3=A9 CC: Wei Liu CC: Stefano Stabellini CC: Julien Grall CC: Volodymyr Babchuk CC: Bertrand Marquis There are other functions which will be good heuristics to annotate, but we probaby want to collect .cold together in one location rather than having t= hem spread out across all translation units. --- xen/include/xen/lib.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/xen/include/xen/lib.h b/xen/include/xen/lib.h index 05ee1e18af6b..11ef287c1ed9 100644 --- a/xen/include/xen/lib.h +++ b/xen/include/xen/lib.h @@ -115,7 +115,7 @@ debugtrace_printk(const char *fmt, ...) {} /* Allows us to use '%p' as general-purpose machine-word format char. */ #define _p(_x) ((void *)(unsigned long)(_x)) extern void printk(const char *format, ...) - __attribute__ ((format (printf, 1, 2))); + __attribute__ ((format (printf, 1, 2), cold)); =20 #define printk_once(fmt, args...) \ ({ \ --=20 2.30.2