Daniel Lezcano wrote: > Pavel Emelyanov wrote: >> Kirill Korotaev wrote: >>> Cedric Le Goater wrote: >>>> Hello Kirill ! >>>> >>>> Kirill Korotaev wrote: >>>>> Pierre, >>>>> >>>>> my point is that after you've added interface "set IPCID", you'll need >>>>> more and more for checkpointing: >>>>> - "create/setup conntrack" (otherwise connections get dropped), >>>>> - "set task start time" (needed for Oracle checkpointing BTW), >>>>> - "set some statistics counters (e.g. networking or taskstats)" >>>>> - "restore inotify" >>>>> and so on and so forth. >>>> right. we know that we will have to handle a lot of these >>>> and more and we will need an API for it :) so how should we handle it ? >>>> through a dedicated syscall that would be able to checkpoint and/or >>>> restart a process, an ipc object, an ipc namespace, a full container ? >>>> will it take a fd or a big binary blob ? >>>> I personally really liked Pavel idea's of filesystem. but we dropped the >>>> thread. >>> Imho having a file system interface means having all its problems. >>> Imagine you have some information about tasks exported with a file system >>> interface. >>> Obviously to collect the information you have to hold some spinlock like >>> tasklist_lock or similar. >>> Obviously, you have to drop the lock between sys_read() syscalls. >>> So interface gets much more complicated - you have to rescan the objects >>> and somehow find the place where >>> you stopped previous read. Or you have to to force reader to read >>> everything at once. >> To remember the place when we stopped previous read we have a "pos" counter >> on the struct file. >> >> Actually, tar utility, that I propose to perform the most simple migration >> reads the directory contents with 4Kb buffer - that's enough for ~500 tasks. >> >> Besides, is this a real problem for a frozen container? > > I like the idea of a C/R filesystem. Does it implies a specific user > space program to orchestrate the checkpoint/restart of the different > subsystems ? I mean the checkpoint is easy but what about the restart ?
I though about smth like "writing to this fs causes restore process". > We must ensure, for example to restore a process before restoring the fd > associated to it, or restore a deleted file before restoring the fd This is achieved by tar automatically - it extracts files in the order of archiving. Thus is we provide them in correct order we'll get them in correct one as well. > opened to it, no ? > > > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
