Messages in this thread Patch in this message | | | Date | Tue, 21 Nov 2000 16:12:17 +0100 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] livelock in elevator scheduling |
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On Tue, Nov 21, 2000 at 05:28:40PM +0900, kumon@flab.fujitsu.co.jp wrote: > @@ -47,6 +47,11 @@ > break; > tmp->elevator_sequence--; > } > + if (entry == head) { > + tmp = blkdev_entry_to_request(entry); > + if (IN_ORDER(req, tmp)) > + entry = real_head->prev; > + } > list_add(&req->queue, entry); > }
This patch is buggy. head with scsi doesn't point to a request so it doesn't make sense to compare it.
> To implement a complete elevator scheduling, preparing an alternate
Complete elevator scheduling is _just_ implemented, but it's enterely disabled. You should always enable it before running a 2.4.x kernel. To do that use elvtune or apply this patch:
--- 2.4.0-test11-pre6/include/linux/elevator.h.~1~ Wed Jul 19 06:43:10 2000 +++ 2.4.0-test11-pre6/include/linux/elevator.h Tue Nov 21 15:57:51 2000 @@ -100,8 +100,8 @@ ((elevator_t) { \ 0, /* not used */ \ \ - 1000000, /* read passovers */ \ - 2000000, /* write passovers */ \ + 500, /* read passovers */ \ + 1000, /* write passovers */ \ 0, /* max_bomb_segments */ \ \ 0, /* not used */ \
The "DoS" attack is the bug that is been fixed by implementing the new elevator with proper scheduling.
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