Jes Sorensen wrote:
"Shailabh" == Shailabh Nagar <[email protected]> writes:
Shailabh> delayacct-setup.patch Initialization code related to
Shailabh> collection of per-task "delay" statistics which measure how
Shailabh> long it had to wait for cpu, sync block io, swapping
Shailabh> etc. The collection of statistics and the interface are in
Shailabh> other patches. This patch sets up the data structures and
Shailabh> allows the statistics collection to be disabled through a
Shailabh> kernel boot paramater.
Shailabh> +#ifdef CONFIG_TASK_DELAY_ACCT
Shailabh> +struct task_delay_info {
Shailabh> + spinlock_t lock;
Shailabh> +
Shailabh> + /* For each stat XXX, add following, aligned appropriately
Shailabh> + *
Shailabh> + * struct timespec XXX_start, XXX_end;
Shailabh> + * u64 XXX_delay;
Shailabh> + * u32 XXX_count;
Shailabh> + */
Shailabh> +};
Shailabh> +#endif
Hmmm
I thought you were going to change this to do
u64 some_delay
u32 foo_count
u32 bar_count
u64 another_delay
To avoid wasting space on 64 bit platforms.
Well, the "aligned appropriately" part of the comment was intended to let
future users know that something like the above should be done.
e.g in a subsequent patch (5/9)
http://www.uwsg.indiana.edu/hypermail/linux/kernel/0603.1/1919.html
when we introduce the additional stat swapin_delay/count, a 64-bit friendly
alignment is being done thus:
u64 blkio_delay; /* wait for sync block io completion */
+ u64 swapin_delay; /* wait for sync block io completion */
u32 blkio_count;
+ u32 swapin_count;
The need for each stat, potentially, to need a separate set of timespec
variables
to reduce nesting problems does introduce another wrinkle in
cache-friendliness
since you'd ideally like to have all the XXX_* variables close together.
Right now
we're good since swapin doesn't need extra timespecs of its own. But future
additions might need to be more careful.
--Shailabh
Jes
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