[lkml]   [2007]   [Apr]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [REPORT] cfs-v4 vs sd-0.44

    * Linus Torvalds <> wrote:

    > but the point I'm trying to make is that X shouldn't get more CPU-time
    > because it's "more important" (it's not: and as noted earlier,
    > thinking that it's more important skews the problem and makes for too
    > *much* scheduling). X should get more CPU time simply because it
    > should get it's "fair CPU share" relative to the *sum* of the clients,
    > not relative to any client individually.

    yeah. And this is not a pipe dream and i think it does not need a
    'wakeup matrix' or other complexities.

    I am --->.<---- this close to being able to do this very robustly under
    CFS via simple rules of economy and trade: there the p->wait_runtime
    metric is intentionally a "physical resource" of "hard-earned right to
    execute on the CPU, by having waited on it" the sum of which is bound
    for the whole system.

    So while with other, heuristic approaches we always had the problem of
    creating a "hyper-inflation" of an uneconomic virtual currency that
    could be freely printed by certain tasks, in CFS the economy of this is
    strict and the finegrained plus/minus balance is strictly managed by a
    conservative and independent central bank.

    So we can actually let tasks "trade" in these very physical units of
    "right to execute on the CPU". A task giving it to another task means
    that this task _already gave up CPU time in the past_. So it's the
    robust equivalent of an economy's "money earned" concept, and this
    "money"'s distribution (and redistribution) is totally fair and totally
    balanced and is not prone to "inflation".

    The "give scheduler money" transaction can be both an "implicit
    transaction" (for example when writing to UNIX domain sockets or
    blocking on a pipe, etc.), or it could be an "explicit transaction":
    sched_yield_to(). This latter i've already implemented for CFS, but it's
    much less useful than the really significant implicit ones, the ones
    which will help X.

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2007-04-23 21:17    [W:0.022 / U:242.060 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site