From: Michal Hocko <mhocko@kernel.org>
To: Fuqian Huang <huangfq.daxian@gmail.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Is it safe to kmalloc a large size of memory in interrupt handler?
Date: Mon, 5 Aug 2019 14:13:14 +0200 [thread overview]
Message-ID: <20190805121314.GN7597@dhcp22.suse.cz> (raw)
In-Reply-To: <CABXRUiSuZc+W7884ek9YifKdx1eiJ_pmyRM42KK0ZhSK9xTkFw@mail.gmail.com>
On Mon 05-08-19 19:57:54, Fuqian Huang wrote:
> In the implementation of kmalloc.
> when the allocated size is larger than KMALLOC_MAX_CACHE_SIZE,
> it will call kmalloc_large to allocate the memory.
> kmalloc_large ->
> kmalloc_order_trace->kmalloc_order->alloc_pages->alloc_pages_current->alloc_pages_nodemask->get_page_from_freelist->node_reclaim->__node_reclaim->shrink_node->shrink_node_memcg->get_scan_count
You shouldn't really get there when using GFP_NOWAIT/GFP_ATOMIC.
> get_scan_count will call spin_unlock_irq which enables local interrupt.
> As the local interrupt should be disabled in the interrupt handler.
> It is safe to use kmalloc to allocate a large size of memory in
> interrupt handler?
It will work very unreliably because larger physically contiguous memory
is not generally available without doing compaction after a longer
runtime. In general I would recommend to use pre allocated buffers or
defer the actual handling to a less restricted context if possible.
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2019-08-05 12:13 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-05 11:57 Is it safe to kmalloc a large size of memory in interrupt handler? Fuqian Huang
2019-08-05 12:13 ` Michal Hocko [this message]
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