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SubjectRe: [PATCH] add a clear_pages function to clear pages of higher order
On Thu, 24 Mar 2005, David Mosberger wrote:

> That's definitely the case. See my earlier post on this topic:
>
> http://www.gelato.unsw.edu.au/linux-ia64/0409/11012.html
>
> Unfortunately, nobody reported any results for larger machines and/or
> more interesting workloads, so the patch is in limbo at this time.
> Clearly, if the CPU that's clearing the page is likely to use that
> same page soon after, it'd be useful to use temporal stores.

Here are some numbers using lmbench of temporal writes vs. non temporal
writes on ia64 (8p machine but lmbench run only for one load). There seems
to be some benefit for fork/exec but overall this does not seem to be a
clear win. I suspect that the distinction between temporal vs. nontemporal
writes is be more beneficial on machines with smaller pagesizes since
the likelyhood that most cachelines of a page are used soon is increased
and therefore hot zeroing is more beneficial.


L M B E N C H 3 . 0 S U M M A R Y
------------------------------------
(Alpha software, do not distribute)

Basic system parameters
-------------------------------------------------------------------------------------------
Host OS Description Mhz tlb cache mem scal
pages line par load
bytes
--------- ------------------------- ----------------------- ---- ----- ----- ------ ----
margin Linux 2.6.12-rc1-bk3 ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3 ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3 ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3 ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3 ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3 ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3 ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3-dm ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3-dm ia64-linux-gnu 1300 128 1
margin Linux 2.6.12-rc1-bk3-dm ia64-linux-gnu 1300 128 1

Processor, Processes - times in microseconds - smaller is better
------------------------------------------------------------------------------------------
Host OS Mhz null null open slct sig sig fork exec sh
call I/O stat clos TCP inst hndl proc proc proc
--------- ------------------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
margin Linux 2.6.12-rc1-bk3 1300 0.04 0.26 4.90 6.11 15.7 0.39 2.43 528. 1926 4853
margin Linux 2.6.12-rc1-bk3 1300 0.04 0.27 4.86 6.10 15.7 0.39 2.45 522. 1910 4260
margin Linux 2.6.12-rc1-bk3 1300 0.04 0.26 4.85 6.10 15.8 0.39 2.40 526. 1916 4429
margin Linux 2.6.12-rc1-bk3 1300 0.04 0.26 4.84 6.11 15.7 0.39 2.40 531. 1838 4429
margin Linux 2.6.12-rc1-bk3 1300 0.04 0.26 4.85 6.11 15.8 0.39 2.47 553. 1931 5118
margin Linux 2.6.12-rc1-bk3 1300 0.04 0.26 5.09 6.37 15.7 0.39 2.40 537. 1934 5133
margin Linux 2.6.12-rc1-bk3 1300 0.04 0.26 5.09 6.35 15.8 0.39 2.40 555. 1939 5389
margin Linux 2.6.12-rc1-bk3-dm 1300 0.04 0.26 4.88 6.10 15.8 0.39 2.42 519. 1829 4787
margin Linux 2.6.12-rc1-bk3-dm 1300 0.04 0.26 4.87 6.09 15.8 0.39 2.40 516. 1830 5057
margin Linux 2.6.12-rc1-bk3-dm 1300 0.04 0.27 4.86 6.10 15.8 0.39 2.40 512. 1878 5166

Context switching - times in microseconds - smaller is better
-------------------------------------------------------------------------------------
Host OS 2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/64K
ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw
--------- ------------------------- ------ ------ ------ ------ ------ ------- -------
margin Linux 2.6.12-rc1-bk3 7.3300 2.7400 7.0400 4.4600 6.6200 3.94000 8.38000
margin Linux 2.6.12-rc1-bk3 7.6100 8.1000 7.3200 4.5900 7.1700 5.50000 7.84000
margin Linux 2.6.12-rc1-bk3 7.2400 8.0000 7.2100 4.3800 6.7500 4.77000 7.37000
margin Linux 2.6.12-rc1-bk3 7.4100 8.0400 7.0500 4.5100 7.2500 4.11000 7.03000
margin Linux 2.6.12-rc1-bk3 7.2600 8.2100 7.2400 4.6500 6.6500 4.08000 7.81000
margin Linux 2.6.12-rc1-bk3 7.4600 7.9000 7.3800 4.3800 6.6200 4.83000 7.27000
margin Linux 2.6.12-rc1-bk3 7.4400 8.2000 7.2000 5.8700 6.8000 4.86000 7.95000
margin Linux 2.6.12-rc1-bk3-dm 7.4400 8.3100 7.1300 5.6900 6.6500 5.49000 7.49000
margin Linux 2.6.12-rc1-bk3-dm 2.1300 8.0100 7.3800 4.6700 6.5500 4.22000 8.16000
margin Linux 2.6.12-rc1-bk3-dm 7.4900 8.1200 2.1500 4.3600 6.6900 5.54000 7.38000

*Local* Communication latencies in microseconds - smaller is better
---------------------------------------------------------------------------------
Host OS 2p/0K Pipe AF UDP RPC/ TCP RPC/ TCP
ctxsw UNIX UDP TCP conn
--------- ------------------------- ----- ----- ---- ----- ----- ----- ----- ----
margin Linux 2.6.12-rc1-bk3 7.330 16.9 24.8 29.6 36.0 31.4 49.5 52.
margin Linux 2.6.12-rc1-bk3 7.610 17.4 22.0 31.5 52.
margin Linux 2.6.12-rc1-bk3 7.240 17.5 21.6 31.3 53.
margin Linux 2.6.12-rc1-bk3 7.410 17.6 11.8 31.2 51.
margin Linux 2.6.12-rc1-bk3 7.260 17.1 20.6 28.2 37.6 51.0 99.7 92.
margin Linux 2.6.12-rc1-bk3 7.460 17.0 21.0 30.2 69.5 35.3 77.4 52.
margin Linux 2.6.12-rc1-bk3 7.440 39.7 19.8 29.1 65.3 34.3 44.8 53.
margin Linux 2.6.12-rc1-bk3-dm 7.440 17.4 20.5 29.4 37.0 34.3 86.7 77.
margin Linux 2.6.12-rc1-bk3-dm 2.130 17.8 20.6 28.7 37.2 31.8 44.9 77.
margin Linux 2.6.12-rc1-bk3-dm 7.490 17.5 11.3 29.0 37.4 77.1 46.1 53.

File & VM system latencies in microseconds - smaller is better
-------------------------------------------------------------------------------------------
Host OS 0K File 10K File Mmap Prot Page 100fd
Create Delete Create Delete Latency Fault Fault selct
--------- ------------------------- ------ ------ ------ ------ ------- ----- ------- -----
margin Linux 2.6.12-rc1-bk3 340.0 0.162 1.26430 10.6
margin Linux 2.6.12-rc1-bk3 339.0 0.176 1.26310 10.5
margin Linux 2.6.12-rc1-bk3 342.0 0.180 1.25700 10.5
margin Linux 2.6.12-rc1-bk3 341.0 0.207 1.25640 10.5
margin Linux 2.6.12-rc1-bk3 339.0 0.166 1.26310 10.6
margin Linux 2.6.12-rc1-bk3 343.0 0.159 1.26350 10.6
margin Linux 2.6.12-rc1-bk3 339.0 0.174 1.25660 10.6
margin Linux 2.6.12-rc1-bk3-dm 340.0 0.185 1.26090 10.6
margin Linux 2.6.12-rc1-bk3-dm 340.0 0.128 1.26310 10.5
margin Linux 2.6.12-rc1-bk3-dm 343.0 0.159 1.25960 10.5

*Local* Communication bandwidths in MB/s - bigger is better
-----------------------------------------------------------------------------------------
Host OS Pipe AF TCP File Mmap Bcopy Bcopy Mem Mem
UNIX reread reread (libc) (hand) read write
--------- ------------------------- ---- ---- ---- ------ ------ ------ ------ ---- -----
margin Linux 2.6.12-rc1-bk3 1172 1826 562. 1732.6 573.5 535.7 284.9 521. 514.7
margin Linux 2.6.12-rc1-bk3 1169 1883 868. 1733.5 573.8 535.2 283.9 521. 514.6
margin Linux 2.6.12-rc1-bk3 1149 1897 654. 1725.5 573.6 535.1 285.2 521. 514.7
margin Linux 2.6.12-rc1-bk3 1167 1883 921. 1726.1 573.8 534.9 283.1 521. 514.7
margin Linux 2.6.12-rc1-bk3 1167 1146 413. 1726.8 573.6 535.4 283.6 522. 515.1
margin Linux 2.6.12-rc1-bk3 1156 1875 905. 1721.7 573.9 535.4 283.8 521. 515.0
margin Linux 2.6.12-rc1-bk3 1103 1741 493. 1727.7 573.6 534.8 283.3 521. 514.8
margin Linux 2.6.12-rc1-bk3-dm 1160 1361 886. 1718.7 573.6 535.0 284.7 521. 514.8
margin Linux 2.6.12-rc1-bk3-dm 1166 1759 665. 1733.0 565.0 535.2 284.6 521. 514.8
margin Linux 2.6.12-rc1-bk3-dm 1140 1879 606. 1706.6 573.6 535.1 283.5 521. 514.6

patch:

Index: linux-2.6.11/arch/ia64/lib/clear_page.S
===================================================================
--- linux-2.6.11.orig/arch/ia64/lib/clear_page.S 2005-03-01 23:37:47.000000000 -0800
+++ linux-2.6.11/arch/ia64/lib/clear_page.S 2005-03-31 14:25:17.000000000 -0800
@@ -43,7 +43,7 @@ GLOBAL_ENTRY(clear_page)
adds dst1 = 16, in0
adds dst2 = 32, in0
;;
-.fetch: stf.spill.nta [dst_fetch] = f0, L3_LINE_SIZE
+.fetch: stf.spill [dst_fetch] = f0, L3_LINE_SIZE
adds dst3 = 48, in0 // executing this multiple times is harmless
br.cloop.sptk.few .fetch
;;
@@ -53,23 +53,23 @@ GLOBAL_ENTRY(clear_page)
;;
#ifdef CONFIG_ITANIUM
// Optimized for Itanium
-1: stf.spill.nta [dst1] = f0, 64
- stf.spill.nta [dst2] = f0, 64
+1: stf.spill [dst1] = f0, 64
+ stf.spill [dst2] = f0, 64
cmp.lt p8,p0=dst_fetch, dst_last
;;
#else
// Optimized for McKinley
-1: stf.spill.nta [dst1] = f0, 64
- stf.spill.nta [dst2] = f0, 64
- stf.spill.nta [dst3] = f0, 64
- stf.spill.nta [dst4] = f0, 128
+1: stf.spill [dst1] = f0, 64
+ stf.spill [dst2] = f0, 64
+ stf.spill [dst3] = f0, 64
+ stf.spill [dst4] = f0, 128
cmp.lt p8,p0=dst_fetch, dst_last
;;
- stf.spill.nta [dst1] = f0, 64
- stf.spill.nta [dst2] = f0, 64
+ stf.spill [dst1] = f0, 64
+ stf.spill [dst2] = f0, 64
#endif
- stf.spill.nta [dst3] = f0, 64
-(p8) stf.spill.nta [dst_fetch] = f0, L3_LINE_SIZE
+ stf.spill [dst3] = f0, 64
+(p8) stf.spill [dst_fetch] = f0, L3_LINE_SIZE
br.cloop.sptk.few 1b
;;
mov ar.lc = saved_lc // restore lc
-
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