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drm: Use a little stash on the stack to avoid kmalloc in most DRM ioctls. 

The kmalloc was taking up about 1.5% of the CPU on an ioctl-heavy workload
(x11perf -aa10text on 965).  Initial results look like they have a
corresponding improvement in performance for aa10text, but more numbers might
not hurt.

Thanks to ajax for pointing out this performance regression I'd introduced
back in 2007.

[airlied: well I introduced it sneakily inside Eric's patch]

Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>
hifive-unleashed-5.1
Eric Anholt 2009-03-19 18:56:14 -07:00 committed by Dave Airlie
parent af7ae351ad
commit 955a23eb3c
1 changed files with 10 additions and 5 deletions
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15
drivers/gpu/drm/drm_drv.c
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@ -421,6 +421,7 @@ int drm_ioctl(struct inode *inode, struct file *filp,
drm_ioctl_t *func;
unsigned int nr = DRM_IOCTL_NR(cmd);
int retcode = -EINVAL;
char stack_kdata[128];
char *kdata = NULL;
atomic_inc(&dev->ioctl_count);
@ -459,10 +460,14 @@ int drm_ioctl(struct inode *inode, struct file *filp,
retcode = -EACCES;
} else {
if (cmd & (IOC_IN | IOC_OUT)) {
kdata = kmalloc(_IOC_SIZE(cmd), GFP_KERNEL);
if (!kdata) {
retcode = -ENOMEM;
goto err_i1;
if (_IOC_SIZE(cmd) <= sizeof(stack_kdata)) {
kdata = stack_kdata;
} else {
kdata = kmalloc(_IOC_SIZE(cmd), GFP_KERNEL);
if (!kdata) {
retcode = -ENOMEM;
goto err_i1;
}
}
}
@ -483,7 +488,7 @@ int drm_ioctl(struct inode *inode, struct file *filp,
}
err_i1:
if (kdata)
if (kdata != stack_kdata)
kfree(kdata);
atomic_dec(&dev->ioctl_count);
if (retcode)