RE: [Xen-ia64-devel] [PATCH] shrink vtlb size

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

Indeed good improvement.
Anthony

-----Original Message-----
From: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Kouya Shimura
Sent: 2007年8月15日 15:13
To: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-ia64-devel] [PATCH] shrink vtlb size

Hi,

I observed usage ratio of vtlb by using the attached
modification (test_vtlb.diff).
It's very low. vtlb includes at most 21 entries.

The attached patch shrinks the default vtlb size from 512KB to 16KB
to optimize memory. Also speedup ptc_e emulation.
To improve the hash function, frequency of collision never changed
and there is no performance degradation.

The following is a result:

xm dmesg | sort | uniq -c
=============================================================
w/o patch (vtlb:512KB)
Linux:
      1 (XEN) thash_purge_all entries:6 collisions:0
      4 (XEN) thash_purge_all entries:7 collisions:0
     10 (XEN) thash_purge_all entries:8 collisions:0
      9 (XEN) thash_purge_all entries:9 collisions:0
      4 (XEN) thash_purge_all entries:10 collisions:0
      1 (XEN) thash_purge_all entries:11 collisions:0
      1 (XEN) thash_purge_all entries:17 collisions:0
      1 (XEN) thash_purge_all entries:20 collisions:0
      1 (XEN) thash_purge_all entries:20 collisions:3

Windows:
     75 (XEN) thash_purge_all entries:1 collisions:0
    228 (XEN) thash_purge_all entries:2 collisions:0
     19 (XEN) thash_purge_all entries:3 collisions:0
     18 (XEN) thash_purge_all entries:4 collisions:0
      5 (XEN) thash_purge_all entries:5 collisions:0
      4 (XEN) thash_purge_all entries:6 collisions:0
      2 (XEN) thash_purge_all entries:7 collisions:0
      9 (XEN) thash_purge_all entries:8 collisions:0
      8 (XEN) thash_purge_all entries:9 collisions:0
      4 (XEN) thash_purge_all entries:10 collisions:0
      2 (XEN) thash_purge_all entries:13 collisions:0
      1 (XEN) thash_purge_all entries:14 collisions:0
      1 (XEN) thash_purge_all entries:16 collisions:0
      1 (XEN) thash_purge_all entries:21 collisions:0

=============================================================
w patch (vtlb:16KB)
Linux:
      4 (XEN) thash_purge_all entries:7 collisions:0
      6 (XEN) thash_purge_all entries:8 collisions:0
      3 (XEN) thash_purge_all entries:9 collisions:0
     10 (XEN) thash_purge_all entries:10 collisions:0
      1 (XEN) thash_purge_all entries:11 collisions:0
      3 (XEN) thash_purge_all entries:11 collisions:1
      2 (XEN) thash_purge_all entries:12 collisions:0
      1 (XEN) thash_purge_all entries:17 collisions:1
      1 (XEN) thash_purge_all entries:19 collisions:1
      1 (XEN) thash_purge_all entries:21 collisions:0

Windows:
     90 (XEN) thash_purge_all entries:1 collisions:0
    230 (XEN) thash_purge_all entries:2 collisions:0
     19 (XEN) thash_purge_all entries:3 collisions:0
      9 (XEN) thash_purge_all entries:4 collisions:0
      6 (XEN) thash_purge_all entries:6 collisions:0
      2 (XEN) thash_purge_all entries:7 collisions:0
     10 (XEN) thash_purge_all entries:8 collisions:0
      7 (XEN) thash_purge_all entries:9 collisions:0
      4 (XEN) thash_purge_all entries:10 collisions:0
      2 (XEN) thash_purge_all entries:13 collisions:0
      1 (XEN) thash_purge_all entries:15 collisions:0
      1 (XEN) thash_purge_all entries:16 collisions:0
      1 (XEN) thash_purge_all entries:21 collisions:0

Thanks,
Kouya

Singed-off-by: Kouya Shimura <kouya@xxxxxxxxxxxxxx>

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