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Re: Performance hit in qemu-system-ppc

From: BALATON Zoltan
Subject: Re: Performance hit in qemu-system-ppc
Date: Tue, 28 Jan 2020 13:48:00 +0100 (CET)
User-agent: Alpine 2.22 (BSF 395 2020-01-19)


cc-ing the ppc list, maintainer and original author of the patch could increase the chances that they actually see your message which they might miss on qemu-devel. David explicitely said he usually cannot read all mails on qemu-devel so likely should be cc-d on all PPC issues (or also cc the qemu-ppc list besides qemu-devel).


On Sun, 26 Jan 2020, Howard Spoelstra wrote:

I noticed a considerable (~20%) slowdown in the cpu performance of
Bisecting led me to this commit:

d03f140804b345a85973976506492027f703d82d is the first bad commit
commit d03f140804b345a85973976506492027f703d82d
Author: Richard Henderson <address@hidden>
Date:   Mon Dec 9 13:49:58 2019 -0800

   cputlb: Move body of cpu_ldst_template.h out of line

   With the tracing hooks, the inline functions are no longer
   so simple.  Once out-of-line, the current tlb_entry lookup
   is redundant with the one in the main load/store_helper.

   This also begins the introduction of a new target facing
   interface, with suffix *_mmuidx_ra.  This is not yet
   official because the interface is not done for user-only.

   Use abi_ptr instead of target_ulong in preparation for
   user-only; the two types are identical for softmmu.

   What remains in cpu_ldst_template.h are the expansions
   for _code, _data, and MMU_MODE<N>_SUFFIX.

   Tested-by: Philippe Mathieu-Daudé <address@hidden>
   Signed-off-by: Richard Henderson <address@hidden>

accel/tcg/cputlb.c               | 116 ++++++++++++++++++++++++++++++++++++
include/exec/cpu_ldst.h          |  25 +++++++-
include/exec/cpu_ldst_template.h | 125
3 files changed, 166 insertions(+), 100 deletions(-)

Thanks for looking into this issue,

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