Linked by Thom Holwerda on Sat 28th Jun 2008 22:09 UTC, submitted by diegocg
X11, Window Managers "Maybe I'm just naive, but designing a graphics API such that all image data had to be sent over a socket to another process every time the image needed to be drawn seems like complete idiocy. Unfortunately, that is precisely what the X Window System forces a program to do, and exactly what Cairo does when drawing images in Linux - a full copy of the image data, send to another process, no less, every time it is drawn. One would think there would be some room for improvement. Unsurprisingly, others felt the same way about X, and decided to write an extension, Xlib Shm or XShm for short, that allows images to placed in a shared memory segment from which the X server reads which allows the program to avoid the memory copy. GTK already makes use of the XShm extension, and it seems like a good idea to see if Gecko couldn't do the same."
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RE[4]: Exaggerating
by BSDfan on Sun 29th Jun 2008 14:18 UTC in reply to "RE[3]: Exaggerating"
BSDfan
Member since:
2007-03-14

My Pentium 4 system running OpenBSD 4.3 (r128 driver):

$ x11perf -putimage500
x11perf - X11 performance program, version 1.5
The X.Org Foundation server version 10400090 on :0.0
from xxx.xxx
Sun Jun 29 10:04:07 2008

Sync time adjustment is 0.0857 msecs.

320 reps @ 16.6892 msec ( 59.9/sec): PutImage 500x500 square
320 reps @ 16.6960 msec ( 59.9/sec): PutImage 500x500 square
320 reps @ 16.7091 msec ( 59.8/sec): PutImage 500x500 square
320 reps @ 16.7655 msec ( 59.6/sec): PutImage 500x500 square
320 reps @ 16.6939 msec ( 59.9/sec): PutImage 500x500 square
1600 trep @ 16.7108 msec ( 59.8/sec): PutImage 500x500 square

$ x11perf -shmput500
x11perf - X11 performance program, version 1.5
The X.Org Foundation server version 10400090 on :0.0
from xxx.xxx
Sun Jun 29 10:04:44 2008

Sync time adjustment is 0.0856 msecs.

1600 reps @ 3.4037 msec ( 294.0/sec): ShmPutImage 500x500 square
1600 reps @ 3.4092 msec ( 293.0/sec): ShmPutImage 500x500 square
1600 reps @ 3.4257 msec ( 292.0/sec): ShmPutImage 500x500 square
1600 reps @ 3.4064 msec ( 294.0/sec): ShmPutImage 500x500 square
1600 reps @ 3.4086 msec ( 293.0/sec): ShmPutImage 500x500 square
8000 trep @ 3.4107 msec ( 293.0/sec): ShmPutImage 500x500 square

I definitely see a speed increase, stop thinking about how well it'll improve performance on modern systems and realize people DO use older systems. (Not that the pentium 4 is is ancient, but I don't have my Alpha system nearby.)

EDIT: This does not in any way mean I'm against the Networking principles of X, but for a local workstation that won't be listening on TCP. (i.e: -nolisten tcp), local optimizations are a good idea.

Edited 2008-06-29 14:22 UTC

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