On 19 March 2014 13:41, Peter Zijlstra peterz@infradead.org wrote:
The keyboard deity gave us delete, please apply graciously when replying to large emails.
On Wed, Mar 19, 2014 at 11:27:12AM +0000, Dietmar Eggemann wrote:
On 18/03/14 17:56, Vincent Guittot wrote:
if (sd->flags & SD_SHARE_CPUPOWER) {sd->imbalance_pct = 110;sd->smt_gain = 1178; /* ~15% */sd->flags |= arch_sd_sibling_asym_packing();} else if (sd->flags & SD_SHARE_PKG_RESOURCES) {sd->imbalance_pct = 117;sd->cache_nice_tries = 1;sd->busy_idx = 2;+#ifdef CONFIG_NUMA
} else if (sd->flags & SD_NUMA) {sd->cache_nice_tries = 2;sd->busy_idx = 3;sd->idle_idx = 2;sd->flags |= SD_SERIALIZE;if (sched_domains_numa_distance[tl->numa_level] > RECLAIM_DISTANCE) {sd->flags &= ~(SD_BALANCE_EXEC |SD_BALANCE_FORK |SD_WAKE_AFFINE);}+#endif
} else {sd->flags |= SD_PREFER_SIBLING;sd->cache_nice_tries = 1;sd->busy_idx = 2;sd->idle_idx = 1;}This 'if ... else statement' is still a weak point from the perspective of making the code robust:
<snip>
Is there a way to check that MC and GMC have to have SD_SHARE_PKG_RESOURCES set so that this can't happen unnoticed?
So from the core codes perspective those names mean less than nothing. Its just a string to carry along for us meat-bags. The string isn't even there when !SCHED_DEBUG.
So from this codes POV you told it it had a domain without PKGSHARE, that's fine.
That said; yeah the thing isn't the prettiest piece of code. But it has the big advantage of being the one place where we convert topology into behaviour.
We might add a check of the child in sd_init to ensure that the child has at least some properties of the current level. I mean that if a level has got the SD_SHARE_PKG_RESOURCES flag, its child must also have it. The same for SD_SHARE_CPUPOWER and SD_ASYM_PACKING.
so we can add something like the below in sd_init
child_flags = SD_SHARE_PKG_RESOURCES | SD_SHARE_CPUPOWER | SD_ASYM_PACKING flags = sd->flags & child_flags if (sd->child) child_flags &= sd->child->flags child_flags &= flags if (flags != child_flags) pr_info("The topology description looks strange \n");
Vincent