| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <56D43F33.4030702@c-s.fr> Date: Mon, 29 Feb 2016 13:53:07 +0100 From: Christophe Leroy <christophe.leroy@....fr> To: Scott Wood <scottwood@...escale.com> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>, linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org Subject: Re: [PATCH 6/9] powerpc32: optimise a few instructions in csum_partial() Le 23/10/2015 05:30, Scott Wood a écrit : > On Tue, 2015-09-22 at 16:34 +0200, Christophe Leroy wrote: >> r5 does contain the value to be updated, so lets use r5 all way long >> for that. It makes the code more readable. >> >> To avoid confusion, it is better to use adde instead of addc >> >> The first addition is useless. Its only purpose is to clear carry. >> As r4 is a signed int that is always positive, this can be done by >> using srawi instead of srwi >> >> Let's also remove the comment about bdnz having no overhead as it >> is not correct on all powerpc, at least on MPC8xx >> >> In the last part, in our situation, the remaining quantity of bytes >> to be proceeded is between 0 and 3. Therefore, we can base that part >> on the value of bit 31 and bit 30 of r4 instead of anding r4 with 3 >> then proceding on comparisons and substractions. >> >> Signed-off-by: Christophe Leroy <christophe.leroy@....fr> >> --- >> arch/powerpc/lib/checksum_32.S | 37 +++++++++++++++++-------------------- >> 1 file changed, 17 insertions(+), 20 deletions(-) > Do you have benchmarks for these optimizations? > > -Scott Using mftbl() to get timebase just before and after call to csum_partial(), I get the following on an MPC885: * 78 bytes packets: 9% faster (11,5 to 10,4 tb ticks) * 328 bytes packets: 3% faster (47,9 to 46,5 tb ticks) Christophe > >> diff --git a/arch/powerpc/lib/checksum_32.S b/arch/powerpc/lib/checksum_32.S >> index 3472372..9c12602 100644 >> --- a/arch/powerpc/lib/checksum_32.S >> +++ b/arch/powerpc/lib/checksum_32.S >> @@ -27,35 +27,32 @@ >> * csum_partial(buff, len, sum) >> */ >> _GLOBAL(csum_partial) >> - addic r0,r5,0 >> subi r3,r3,4 >> - srwi. r6,r4,2 >> + srawi. r6,r4,2 /* Divide len by 4 and also clear carry */ >> beq 3f /* if we're doing < 4 bytes */ >> - andi. r5,r3,2 /* Align buffer to longword boundary */ >> + andi. r0,r3,2 /* Align buffer to longword boundary */ >> beq+ 1f >> - lhz r5,4(r3) /* do 2 bytes to get aligned */ >> - addi r3,r3,2 >> + lhz r0,4(r3) /* do 2 bytes to get aligned */ >> subi r4,r4,2 >> - addc r0,r0,r5 >> + addi r3,r3,2 >> srwi. r6,r4,2 /* # words to do */ >> + adde r5,r5,r0 >> beq 3f >> 1: mtctr r6 >> -2: lwzu r5,4(r3) /* the bdnz has zero overhead, so it should */ >> - adde r0,r0,r5 /* be unnecessary to unroll this loop */ >> +2: lwzu r0,4(r3) >> + adde r5,r5,r0 >> bdnz 2b >> - andi. r4,r4,3 >> -3: cmpwi 0,r4,2 >> - blt+ 4f >> - lhz r5,4(r3) >> +3: andi. r0,r4,2 >> + beq+ 4f >> + lhz r0,4(r3) >> addi r3,r3,2 >> - subi r4,r4,2 >> - adde r0,r0,r5 >> -4: cmpwi 0,r4,1 >> - bne+ 5f >> - lbz r5,4(r3) >> - slwi r5,r5,8 /* Upper byte of word */ >> - adde r0,r0,r5 >> -5: addze r3,r0 /* add in final carry */ >> + adde r5,r5,r0 >> +4: andi. r0,r4,1 >> + beq+ 5f >> + lbz r0,4(r3) >> + slwi r0,r0,8 /* Upper byte of word */ >> + adde r5,r5,r0 >> +5: addze r3,r5 /* add in final carry */ >> blr >> >> /*
Powered by blists - more mailing lists