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c2452f3278
struct dentry is one of the most critical structures in the kernel. So it's sad to see it going neglected. With CONFIG_PROFILING turned on (which is probably the common case at least for distros and kernel developers), sizeof(struct dcache) == 208 here (64-bit). This gives 19 objects per slab. I packed d_mounted into a hole, and took another 4 bytes off the inline name length to take the padding out from the end of the structure. This shinks it to 200 bytes. I could have gone the other way and increased the length to 40, but I'm aiming for a magic number, read on... I then got rid of the d_cookie pointer. This shrinks it to 192 bytes. Rant: why was this ever a good idea? The cookie system should increase its hash size or use a tree or something if lookups are a problem. Also the "fast dcookie lookups" in oprofile should be moved into the dcookie code -- how can oprofile possibly care about the dcookie_mutex? It gets dropped after get_dcookie() returns so it can't be providing any sort of protection. At 192 bytes, 21 objects fit into a 4K page, saving about 3MB on my system with ~140 000 entries allocated. 192 is also a multiple of 64, so we get nice cacheline alignment on 64 and 32 byte line systems -- any given dentry will now require 3 cachelines to touch all fields wheras previously it would require 4. I know the inline name size was chosen quite carefully, however with the reduction in cacheline footprint, it should actually be just about as fast to do a name lookup for a 36 character name as it was before the patch (and faster for other sizes). The memory footprint savings for names which are <= 32 or > 36 bytes long should more than make up for the memory cost for 33-36 byte names. Performance is a feature... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
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| accessibility | ||
| acpi | ||
| amba | ||
| ata | ||
| atm | ||
| auxdisplay | ||
| base | ||
| block | ||
| bluetooth | ||
| cdrom | ||
| char | ||
| clocksource | ||
| connector | ||
| cpufreq | ||
| cpuidle | ||
| crypto | ||
| dca | ||
| dio | ||
| dma | ||
| edac | ||
| eisa | ||
| firewire | ||
| firmware | ||
| gpio | ||
| gpu | ||
| hid | ||
| hwmon | ||
| i2c | ||
| ide | ||
| idle | ||
| ieee1394 | ||
| infiniband | ||
| input | ||
| isdn | ||
| leds | ||
| lguest | ||
| macintosh | ||
| mca | ||
| md | ||
| media | ||
| memstick | ||
| message | ||
| mfd | ||
| misc | ||
| mmc | ||
| mtd | ||
| net | ||
| nubus | ||
| of | ||
| oprofile | ||
| parisc | ||
| parport | ||
| pci | ||
| pcmcia | ||
| pnp | ||
| power | ||
| ps3 | ||
| rapidio | ||
| regulator | ||
| rtc | ||
| s390 | ||
| sbus | ||
| scsi | ||
| serial | ||
| sh | ||
| sn | ||
| spi | ||
| ssb | ||
| staging | ||
| tc | ||
| telephony | ||
| thermal | ||
| uio | ||
| usb | ||
| uwb | ||
| video | ||
| virtio | ||
| w1 | ||
| watchdog | ||
| xen | ||
| zorro | ||
| Kconfig | ||
| Makefile | ||