file-operations: throttle page cache during cross-device copies#3726
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KonTy wants to merge 1 commit intolinuxmint:masterfrom
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file-operations: throttle page cache during cross-device copies#3726KonTy wants to merge 1 commit intolinuxmint:masterfrom
KonTy wants to merge 1 commit intolinuxmint:masterfrom
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When copying large files to a slow device (e.g. USB), GLib's splice() fills the page cache at RAM speed. Once dirty pages exceed the kernel's dirty_ratio the kernel blocks all writers, making Nemo (and the whole desktop) appear frozen for minutes. Fix this by periodically calling sync_file_range() + posix_fadvise() from the copy progress callback every 32 MiB: - SYNC_FILE_RANGE_WAIT_BEFORE: provides natural back-pressure by waiting for the previous chunk's writeback to finish, pacing the copy to actual device speed. - SYNC_FILE_RANGE_WRITE: starts async writeback for the new chunk. - POSIX_FADV_DONTNEED: drops pages whose writeback already completed, keeping memory usage bounded. This keeps dirty pages at ~32-64 MiB instead of many gigabytes, the progress bar advances at the real device speed, and no single syscall blocks for more than one 32 MiB chunk. Only affects cross-filesystem copies of regular files (the common fast-source → slow-USB case). Same-filesystem moves and copies are unaffected. Fixes: linuxmint#3710
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This "problem" has never occurred for me. |
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Fixes #3710
When copying many large files (15-20 ISOs, 3-6 GB each) from a fast source (NAS/SSD) to a slow USB drive, GLib's splice() fills the page cache at RAM speed. Once dirty pages hit the kernel's dirty_ratio, all writes block and the system freezes. I've seen the same behavior in Double Commander on Arch, where I have to enable "verify on copy" to make sure files aren't silently corrupted. The fix adds periodic sync_file_range() + posix_fadvise(DONTNEED) calls every 32 MiB in the copy progress callback, which provides natural back-pressure that paces the copy to actual device speed and keeps dirty pages bounded at ~32-64 MiB instead of many gigabytes.