Hi Robert, Thanks for the patch. In the first email in this thread I was proposing the same solution and had asked whether doing this has any side effects. That is how this discussion started. I did some experiments and have got the answers for that. Just for every ones benefit I've re-worded the question again and put the details of the experiment below.
Question: On occasions when we return because of the lock unavailability, what could be the worst case number of ashmem pages that are left unfreed (lru_count). Will it be very huge and have side effects? To get the answer for this question, I added some instrumentation code to ashmem_shrink function on top of the patch. I ran Android monkey tests with lot of memory hungry applications so as to hit the Low Memory situation more frequently. After running this for almost a day I did not see a situation where the shrinker did not have the mutex. In fact what I found is that (in this use case at-least) most of the time the "lru_count" is zero, which means the application has not unpinned the pages. So the shrinker has no job to do (basically shrink_slab does not call ashmem_shrinker second time). So worst case if we hit a scenario where the shrinker is called I'm sure the lru_count would be very low. So even if the shrinker returns without freeing them (because of unavailability of the lock) its not going to be costly. After this experiment, I too think that this patch (returning from ashmem_shrink if the lock is not available) is good enough and does not seem to have any major side effects. PS: Any plans of submitting this patch formally? Warm Regards, Shankar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
